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Force and Laws of Motion PYQs – Physics, SSC & Railway

112 Force and Laws of Motion (Physics) questions asked in recent SSC and Railway exams, newest first, with exam, date & shift, answers and solutions.

📚 112 questionsSSC 32 · Railway 80
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SSC Stenographer 2026 – 15 September 2026 Shift 2 · Conservation of momentum and recoil

Q1. Which of the following best reflects the principle of conservation of linear momentum?

  1. (a) In an isolated system, the total momentum before and after a collision remains constant, regardless of the internal forces.
  2. (b) The total energy in an isolated system remains zero unless acted upon by external forces.
  3. (c) Linear momentum can only be conserved in gravitational fields.
  4. (d) Linear momentum applies only to subatomic particles in a magnetic field.
Answer & solution

Answer: (a) In an isolated system, the total momentum before and after a collision remains constant, regardless of the internal forces.

Answer: Option 1 — In an isolated system, the total momentum before and after a collision remains constant, regardless of the internal forces.
When no external force acts, the internal forces between the bodies come in equal and opposite pairs (Newton's third law), so they cannot change the total momentum.
Hence m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂ for any collision, elastic or not.
Revision note — Momentum and its conservation
• Momentum p = mv; it is a vector with SI unit kg m/s (kg m s⁻¹).
• Newton's second law in its original form: force = rate of change of momentum, F = Δp/Δt; hence impulse = F × t = change in momentum.
• Law of conservation of momentum: in the absence of an external force the total momentum of a system stays constant; it follows directly from the third law.
• Applications: the recoil of a gun, rocket propulsion, a swimmer pushing water backward, and the analysis of collisions.
• In an elastic collision both momentum and kinetic energy are conserved; in an inelastic collision only momentum is conserved and some kinetic energy becomes heat or sound.
• A cricketer lowering his hands while catching, or a car's crumple zone, lengthens the time of impact and so reduces the force for the same change in momentum.
Do not mix these up
• Conservation of momentum vs conservation of energy — momentum is conserved in every collision of an isolated system; kinetic energy is conserved only in an elastic one.
• Momentum vs kinetic energy — p = mv is a vector; KE = ½mv² is a scalar. Doubling the velocity doubles the momentum but quadruples the kinetic energy.
Also asked from this topic: the scenario that best illustrates conservation of momentum (a gun recoiling when a bullet is fired); the formula for momentum (p = mv); its SI unit (kg m/s).
RRB Group D 2025-26 – 25 August 2026 Shift 1 · Conservation of momentum and recoil

Q2. Why does a gun recoil backward when it is fired?

  1. (a) The trigger causes the gun to move backward
  2. (b) The gun is heavy and naturally moves backward
  3. (c) The air resistance pushes the gun backward
  4. (d) The bullet pushes forward, and the gun experiences an equal and opposite backward force
Answer & solution

Answer: (d) The bullet pushes forward, and the gun experiences an equal and opposite backward force

Correct Answer:
Correct Answer: Option 4 – The bullet pushes forward, and the gun experiences an equal and opposite backward force
Explanation:
This is a direct application ofNewton's Third Law of Motion: for every action, there is an equal and opposite reaction. As the gun exerts a forward force on the bullet (action), the bullet exerts an equal and opposite backward force on the gun (reaction), causing the recoil.
Important Facts:
• Recoil is also explained by conservation of momentum — total momentum before firing is zero, so bullet and gun get equal and opposite momenta.
• The gun's recoil velocity is much smaller than the bullet's due to its much larger mass.
RRB Group D 2025-26 – 25 August 2026 Shift 1 · Newton's third law and its applications

Q3. A horse pulls a cart with a force of 500 N. The force experienced by the horse due to the cart is:

  1. (a) 0 N
  2. (b) 500 N equal and opposite to the motion
  3. (c) 250 N
  4. (d) 1000 N
Answer & solution

Answer: (b) 500 N equal and opposite to the motion

Correct Answer:
Correct Answer: Option 2 – 500 N equal and opposite to the motion
Explanation:
ByNewton's Third Law, when the horse pulls the cart forward with a force of 500 N (action), the cart exerts an equal and opposite reaction force of500 Non the horse, directed backward (opposite to the direction of motion).
Important Facts:
• Action and reaction forces are always equal in magnitude and opposite in direction, and act on different bodies.
• The horse is still able to move the cart forward because of the additional frictional grip between its feet and the ground.
RRB Group D 2025-26 – 25 August 2026 Shift 2 · Numericals on force and momentum

Q4. A constant force is applied to a 5 kg object for 4 seconds, causing its velocity to increase from 2 m/s to 10 m/s. What is the magnitude of this force?

  1. (a) 2 N
  2. (b) 10 N
  3. (c) 5 N
  4. (d) 20 N
Answer & solution

Answer: (b) 10 N

Correct Answer:
Correct Answer: Option 2 – 10 N
Explanation:
Acceleration a = (v − u)/t = (10 − 2)/4 = 8/4 = 2 m/s². Using Newton's second law, Force F = m × a = 5 kg × 2 m/s² =10 N.
RRB Group D 2025-26 – 25 August 2026 Shift 3 · Newton's third law and its applications

Q5. What happens to the magnitude of action and reaction forces in Newton’s third law pairs?

  1. (a) They are always equal in magnitude and opposite in direction
  2. (b) They combine to make a stronger force
  3. (c) They cancel each other completely
  4. (d) They depend on which object is heavier
Answer & solution

Answer: (a) They are always equal in magnitude and opposite in direction

Correct Answer:
Correct Answer: Option 1 – They are always equal in magnitude and opposite in direction
Explanation:
Newton's Third Law states that for every action there is an equal and opposite reaction — the two forces in an action-reaction pair are always equal in magnitude and act in opposite directions, on two different bodies, regardless of the masses of the objects involved.
Important Facts:
• Action and reaction forces act on different objects, so they never cancel each other on the same body.
• This law holds regardless of which object is heavier — heavier objects show smaller acceleration for the same force, per Newton's second law.
RRB Group D 2025-26 – 21 August 2026 Shift 1 · Numericals on force and momentum

Q6. If a 2 kg ball initially at rest is pushed with a force of 8 N for 5 seconds, what is its velocity at the end of 5 seconds?

  1. (a) 8 m/s
  2. (b) 5 m/s
  3. (c) 20 m/s
  4. (d) 10 m/s
Answer & solution

Answer: (c) 20 m/s

Explanation:
Using Newton's second law: a = F/m = 8 N / 2 kg = 4 m/s². Using v = u + at with u = 0, t = 5 s: v = 0 + 4×5 = 20 m/s.
Correct Answer: Option 3 – 20 m/s
RRB Group D 2025-26 – 21 August 2026 Shift 1 · Newton's third law and its applications

Q7. Which situation does NOT correctly illustrate an action-reaction pair as per Newton's third law?

  1. (a) A hammer strikes a nail, nail pushes hammer back
  2. (b) A hand pushes a wall, wall pushes hand back
  3. (c) A car accelerating due to its engine
  4. (d) A foot kicks a ball, ball pushes foot back
Answer & solution

Answer: (c) A car accelerating due to its engine

Explanation:
Newton's third law pairs consist of two clearly identified equal-and-opposite forces exerted by two bodies on each other (hammer on nail and nail on hammer; hand on wall and wall on hand; foot on ball and ball on foot). 'A car accelerating due to its engine' describes only a single cause-effect statement about the car's motion — it does not spell out a pair of mutual forces between two interacting bodies, so it does not correctly illustrate an action-reaction pair as phrased.
Correct Answer: Option 3 – A car accelerating due to its engine
RRB Group D 2025-26 – 21 August 2026 Shift 3 · Newton's first law and inertia

Q8. Seat belts in cars are provided to protect passengers during sudden braking or collision because of:

  1. (a) Inertia of direction
  2. (b) Inertia of motion
  3. (c) Friction
  4. (d) Inertia of rest
Answer & solution

Answer: (b) Inertia of motion

Correct Answer:
Correct Answer: Option 2 – Inertia of motion
Explanation:
When a car brakes suddenly, the passenger's body tends to continue moving forward due toinertia of motion(Newton's first law). Seat belts restrain the body, preventing injury.
Important Facts:
• Inertia of rest refers to a resting body resisting a change to motion (e.g., a jerk forward when a stationary vehicle suddenly moves).
RRB Group D 2025-26 – 20 August 2026 Shift 3 · Newton's first law and inertia

Q9. Which scenario best demonstrates the first law of motion as stated by Newton regarding an object’s tendency to maintain its state of at rest or uniform motion?

  1. (a) A tree sways in the wind
  2. (b) A book lying on a table stays still until someone pushes it
  3. (c) A car speeds up as the driver presses the accelerator
  4. (d) A ball rolling down a hill accelerates
Answer & solution

Answer: (b) A book lying on a table stays still until someone pushes it

Correct Answer:
Option 2 – A book lying on a table stays still until someone pushes it
Explanation:
Newton's first law (law of inertia) states that a body at rest remains at rest, and a body in uniform motion continues in that state, unless acted upon by an external force. A book staying still on a table until pushed is a direct demonstration of this tendency (inertia of rest).
RRB Group D 2025-26 – 20 August 2026 Shift 3 · Numericals on force and momentum

Q10. A 6 kg body is subjected to a force that brings it from rest to a velocity of 18 m/s in 3 seconds. What is the value of the force?

  1. (a) 54 N
  2. (b) 36 N
  3. (c) 18 N
  4. (d) 12 N
Answer & solution

Answer: (b) 36 N

Correct Answer:
Option 2 – 36 N
Explanation:
Acceleration a = (v − u)/t = (18 − 0)/3 = 6 m/s². Force F = ma = 6 × 6 =36 N.
RRB Group D 2025-26 – 19 August 2026 Shift 1 · Newton's second law and momentum

Q11. If a car and a truck are pushed with the same force, which will accelerate more according to the second law of motion?

  1. (a) The car will accelerate more
  2. (b) Both will accelerate equally
  3. (c) The truck will accelerate more
  4. (d) Neither will accelerate
Answer & solution

Answer: (a) The car will accelerate more

Correct Answer:
Correct Answer: Option 1 – The car will accelerate more
Explanation:
By Newton's second law,a = F/m. For the same applied force F, acceleration isinversely proportional to mass. Since a car has much less mass than a truck, thecar will accelerate morethan the truck under the same force.
Important Facts:
• Newton's Second Law: F = ma, so a = F/m.
• Greater mass means greater inertia and hence smaller acceleration for a given force.
RRB Group D 2025-26 – 19 August 2026 Shift 3 · Newton's third law and its applications

Q12. According to the Newton’s Third Law of Motion, what happens to a stationary rowing boat when a sailor jumps forward from it?

  1. (a) The boat remains stationary since only the sailor moves.
  2. (b) The boat moves unpredictably due to water resistance.
  3. (c) The boat moves backward due to an equal and opposite reaction force
  4. (d) The boat moves forward along with the sailor.
Answer & solution

Answer: (c) The boat moves backward due to an equal and opposite reaction force

Correct Answer:
Option 3 – The boat moves backward due to an equal and opposite reaction force
Explanation:
According toNewton's Third Law, for every action there is an equal and opposite reaction. When the sailor pushes against the boat to jump forward (action), the boat exerts an equal and opposite force on the sailor, pushing the boatbackward.
Important Facts:
• Newton's Third Law: forces always occur in action-reaction pairs acting on different bodies.
• This principle also explains recoil of a gun when a bullet is fired.
Correct Answer: Option 3 – The boat moves backward due to an equal and opposite reaction force
RRB Group D 2025-26 – 18 August 2026 Shift 2 · Newton's first law and inertia

Q13. When a motorcar makes a sharp turn at a high speed, the passengers tend to get thrown to one side. This can be explained using which of the following laws?

  1. (a) Newton’s Law of Gravitation
  2. (b) Law of static friction
  3. (c) Law of Conservation of Momentum
  4. (d) Newton’s First Law of Motion
Answer & solution

Answer: (d) Newton’s First Law of Motion

Inertia in a Turning Car
When a car makes a sharp turn, the passengers' bodies tend to continue moving in a straight line due toinertia of motion, causing them to be thrown to one side (opposite to the direction of the turn).
This is explained byNewton's First Law of Motion(the law of inertia): a body continues in its state of motion unless acted upon by an external force.
Correct Answer: Newton's First Law of Motion
RRB Group D 2025-26 – 17 August 2026 Shift 1 · Newton's second law and momentum

Q14. A 0.6 kg soccer ball and a 1.0 kg basketball are kicked with the same acceleration. Which will experience a greater force, according to Newton's second law?

  1. (a) The ball with higher acceleration, regardless of mass
  2. (b) Both experience the same force
  3. (c) The soccer ball, because it is lighter
  4. (d) The basketball, because it has greater mass
Answer & solution

Answer: (d) The basketball, because it has greater mass

Newton's Second Law: Force and Mass
Newton's second law:F = m × a. When acceleration is the same for both balls, the force required is directly proportional to mass.
The basketball (1.0 kg) has a greater mass than the soccer ball (0.6 kg), so for the same acceleration, the basketball requires/experiences agreater force(F_basketball = 1.0a > F_soccer = 0.6a).
Correct Answer: The basketball, because it has greater mass
RRB Group D 2025-26 – 17 August 2026 Shift 2 · Impulse

Q15. If a car is gradually pushed to a speed of 1 m/s, what determines the change in its momentum according to the second law of motion?

  1. (a) Both the magnitude of the force and the time during which the force is applied determine the change in momentum.
  2. (b) Only the direction of motion changes the momentum.
  3. (c) Only the mass of the car determines the change in momentum.
  4. (d) The magnitude of force alone is enough to determine the change.
Answer & solution

Answer: (a) Both the magnitude of the force and the time during which the force is applied determine the change in momentum.

Newton's Second Law and Change in Momentum
Newton's second law states F = dp/dt, i.e., the rate of change of momentum is proportional to the applied force. Rearranged, the change in momentum equals impulse = Force × time (Δp = F·t). Therefore,both the magnitude of the force applied and the duration for which it actsdetermine the resulting change in momentum.
• Direction of motion alone does not determine the magnitude of momentum change.
• Mass alone (without force/time) does not determine change in momentum; mass relates force to acceleration, not directly to Δp for a given push.
Correct Answer: Both the magnitude of the force and the time during which the force is applied determine the change in momentum.
RRB Group D 2025-26 – 17 August 2026 Shift 2 · Newton's second law and momentum

Q16. Which situation demonstrates Newton’s second law of motion?

  1. (a) A ball rolling at a constant speed on a flat surface
  2. (b) A swimmer pushes water backward and moves forward
  3. (c) A stationary object resting on a table
  4. (d) A heavy truck requires more force to accelerate than a small car
Answer & solution

Answer: (d) A heavy truck requires more force to accelerate than a small car

Demonstrating Newton's Second Law
Newton's second law states F = ma. For the same acceleration, a larger mass requires a larger force. Aheavy truck needing more force to accelerate than a small cardirectly illustrates this relationship between force, mass, and acceleration.
• A ball rolling at constant speed on a flat surface illustrates Newton's first law (no net force needed to maintain constant velocity).
• A swimmer pushing water backward to move forward illustrates Newton's third law (action-reaction).
• A stationary object on a table illustrates balanced forces (related to the first law), not the second law.
Correct Answer: A heavy truck requires more force to accelerate than a small car
RRB Group D 2025-26 – 14 August 2026 Shift 1 · Newton's third law and its applications

Q17. In a tug-of-war, Team A pulls Team B with a force of 300 N. According to Newton's Third Law, what force does Team B exert on Team A?

  1. (a) 150 N in the same direction
  2. (b) 300 N in the opposite direction
  3. (c) 600 N in the opposite direction
  4. (d) 300 N in the same direction
Answer & solution

Answer: (b) 300 N in the opposite direction

Answer: Option 2 – 300 N in the opposite direction.
• Newton's third law: reaction is equal and opposite ⇒300 N opposite.
RRB Group D 2025-26 – 14 August 2026 Shift 3 · Numericals on force and momentum

Q18. Which situation demonstrates the correct application of the force formula?

  1. (a) A 2 kg object accelerates at 5 m/s squared and a force of 15 N is applied
  2. (b) A 10 kg object accelerates at 1 m/s squared and a force of 5 N is applied
  3. (c) A 4 kg object accelerates at 3 m/s squared and a force of 20 N is applied
  4. (d) A 5 kg object accelerates at 2 m/s squared and a force of 10 N is applied
Answer & solution

Answer: (d) A 5 kg object accelerates at 2 m/s squared and a force of 10 N is applied

Answer: Option 4 – 5 kg object at 2 m/s² with 10 N.
• F = ma = 5 × 2 =10 N— the only correctly matched set.
RRB Group D 2025-26 – 13 August 2026 Shift 3 · Newton's third law and its applications

Q19. During the firing of a gun, the bullet moves forward while the gun recoils backward. Which option correctly identifies the action and the corresponding reaction in this situation?

  1. (a) The gun exerts a forward force on the bullet; the bullet exerts an equal backward force on the gun.
  2. (b) The bullet pushes the gun forward, and the gun pushes the bullet backward.
  3. (c) The gun and bullet both move because the trigger is pulled, not because of action-reaction forces.
  4. (d) The bullet moves forward due to gunpowder only, and the gun moves backward due to its own weight.
Answer & solution

Answer: (a) The gun exerts a forward force on the bullet; the bullet exerts an equal backward force on the gun.

Answer: Option 1 – The gun exerts a forward force on the bullet; the bullet exerts an equal backward force on the gun.
• By Newton's third law, action (gun→bullet forward) and reaction (bullet→gun backward) are equal and opposite (recoil).
RRB Group D 2025-26 – 12 August 2026 Shift 1 · Force, its effects and types

Q20. If an object continues moving in the same direction at the same speed, what can be inferred about the forces acting on it?

  1. (a) The forces are unbalanced
  2. (b) The forces always cancel gravity
  3. (c) All forces are in same direction as direction of motion
  4. (d) The forces are balanced
Answer & solution

Answer: (d) The forces are balanced

Answer: Option 4 – The forces are balanced.
• Constant velocity (same speed, same direction) means net force = 0, i.e.balanced forces.
RRB Group D 2025-26 – 12 August 2026 Shift 2 · Newton's second law and momentum

Q21. A student pushes two carts, one heavy and one light, with the same force. According to Newton's second law, what will happen to their accelerations?

  1. (a) Both carts will accelerate equally
  2. (b) The lighter cart will accelerate more than the heavier cart
  3. (c) The heavier cart will move with zero acceleration
  4. (d) The heavier cart will accelerate more than the lighter cart
Answer & solution

Answer: (b) The lighter cart will accelerate more than the heavier cart

Answer: Option 2 – The lighter cart will accelerate more.
• a = F/m. For the same force, thesmaller mass gets larger acceleration.
RRB Group D 2025-26 – 12 August 2026 Shift 3 · Newton's first law and inertia

Q22. What property of an object does the first law of motion primarily describe?

  1. (a) Momentum
  2. (b) Inertia
  3. (c) Acceleration
  4. (d) Energy
Answer & solution

Answer: (b) Inertia

Answer: Option 2 – Inertia.
• Newton's first law describesinertia– a body's tendency to resist a change in its state of rest or motion.
RRB Group D 2025-26 – 11 August 2026 Shift 1 · Force, its effects and types

Q23. Which scenario best demonstrates an unbalanced force acting on an object?

  1. (a) A car parked at rest in a garage
  2. (b) A picture hanging stationary on a wall
  3. (c) A soccer ball starts rolling after being kicked
  4. (d) A cup sitting on a desk not moving
Answer & solution

Answer: (c) A soccer ball starts rolling after being kicked

Answer: Option 3 – A soccer ball starts rolling after being kicked.
• Anunbalanced forcechanges motion. The kick's net force sets the stationary ball moving; the other options show balanced forces (no motion change).
RRB Group D 2025-26 – 11 August 2026 Shift 1 · Force, its effects and types

Q24. What is the effect of unbalanced forces on an object at rest?

  1. (a) It changes the color of the object
  2. (b) It always increases the mass of the object
  3. (c) It keeps the object at rest
  4. (d) It causes the object to start moving
Answer & solution

Answer: (d) It causes the object to start moving

Answer: Option 4 – It causes the object to start moving.
• A net (unbalanced) force on a resting object produces acceleration, so the objectstarts to move.
RRB Group D 2025-26 – 11 August 2026 Shift 2 · Newton's first law and inertia

Q25. According to the first law of motion, what will happen to a ball rolling on a smooth, horizontal surface if no external force acts on it?

  1. (a) The ball will speed up on its own.
  2. (b) The ball will continue to roll at a constant speed in the same direction.
  3. (c) The ball will gradually slow down and stop by itself.
  4. (d) The ball will change its direction automatically.
Answer & solution

Answer: (b) The ball will continue to roll at a constant speed in the same direction.

Answer: Option 2 – The ball will continue to roll at a constant speed in the same direction.
• By thefirst law (inertia), with no external force the ball keeps moving at constant velocity.
RRB Group D 2025-26 – 11 August 2026 Shift 3 · Newton's first law and inertia

Q26. Why is it difficult to push a heavy box from rest, according to the first law of motion?

  1. (a) The box has no wheels to roll
  2. (b) The box resists changes to its state due to inertia
  3. (c) The box is pulled back by gravity
  4. (d) The box is glued to the floor
Answer & solution

Answer: (b) The box resists changes to its state due to inertia

Answer: Option 2 – The box resists changes to its state due to inertia.
• By the first law, a body at rest resists motion because of itsinertia.
RRB Group D 2025-26 – 11 August 2026 Shift 3 · Force, its effects and types

Q27. Which example indicates that forces acting on an object are balanced?

  1. (a) A ball falling to the ground
  2. (b) A book lying motionless on a shelf
  3. (c) A car accelerating down a road
  4. (d) A ball at rest begins to move
Answer & solution

Answer: (b) A book lying motionless on a shelf

Answer: Option 2 – A book lying motionless on a shelf.
• A stationary book hasbalanced forces(weight = normal reaction), so no motion.
RRB Group D 2025-26 – 10 August 2026 Shift 1 · Newton's second law and momentum

Q28. If the same force is applied to two objects of different masses, what happens to their accelerations?

  1. (a) Both objects will have the same acceleration.
  2. (b) The object with more mass will have greater acceleration.
  3. (c) Acceleration depends only on the force, not on the mass.
  4. (d) The object with less mass will have greater acceleration.
Answer & solution

Answer: (d) The object with less mass will have greater acceleration.

Answer: Option 4 — The object with less mass will have greater acceleration
a = F/m; for the same force,smaller mass ⟹ greater acceleration→ Option 4.
RRB Group D 2025-26 – 10 August 2026 Shift 2 · Numericals on force and momentum

Q29. A car of mass 1000 kg increases its velocity from 10 m/s to 20 m/s in 5 seconds. What is the force exerted on the car?

  1. (a) 1000 N
  2. (b) 2500 N
  3. (c) 1500 N
  4. (d) 2000 N
Answer & solution

Answer: (d) 2000 N

Answer: Option 4 – 2000 N.
• Acceleration a = (v − u)/t = (20 − 10)/5 =2 m/s².
• Force F = m × a = 1000 × 2 =2000 N.
RRB Group D 2025-26 – 10 August 2026 Shift 3 · Numericals on force and momentum

Q30. A force of 60 N is used to push a box, causing it to accelerate at 3 m/s². What is the mass of the box?

  1. (a) 180 kg
  2. (b) 20 kg
  3. (c) 18 kg
  4. (d) 15 kg
Answer & solution

Answer: (b) 20 kg

Answer: Option 2 – 20 kg.
• F = m × a ⇒ m = F/a = 60 ÷ 3 =20 kg.
RRB Group D 2025-26 – 9 August 2026 Shift 1 · Newton's second law and momentum

Q31. If the mass of a body is doubled and acceleration remains constant, the force will:

  1. (a) Become four times
  2. (b) Remain the same
  3. (c) Become double
  4. (d) Become half
Answer & solution

Answer: (c) Become double

Answer: Option 3 — Become double
F = ma. Doubling mass (a constant) doubles the force → Option 3.
RRB Group D 2025-26 – 6 August 2026 Shift 2 · Impulse

Q32. If two bodies of equal mass are acted upon by unequal forces for the same time, then the body on which the larger force acts will have _________.

  1. (a) less change in momentum
  2. (b) no change in momentum
  3. (c) equal change in momentum
  4. (d) more change in momentum
Answer & solution

Answer: (d) more change in momentum

Answer: Option 4 — more change in momentum
Impulse = F × t = change in momentum. For equal time, thelarger forcegives agreater change in momentum→ Option 4.
RRB Group D 2025-26 – 5 August 2026 Shift 3 · Numericals on force and momentum

Q33. A car with a mass 2000 kg accelerates at 4 m/s². According to Newton's Second Law, what is the magnitude of the force applied to the car?

  1. (a) 1000 N
  2. (b) 2500 N
  3. (c) 500 N
  4. (d) 8000 N
Answer & solution

Answer: (d) 8000 N

Answer: Option 4 — 8000 N
F = ma = 2000 × 4 =8000 N→ Option 4.
RRB Group D 2025-26 – 4 August 2026 Shift 1 · Newton's third law and its applications

Q34. Two ice skaters push off from each other on a frictionless surface. What will be observed about their motion?

  1. (a) Both skaters move away from each other in opposite directions with equal and opposite forces.
  2. (b) Both skaters move together in the same direction.
  3. (c) One skater moves while the other remains stationary.
  4. (d) Both skaters move in circles around each other.
Answer & solution

Answer: (a) Both skaters move away from each other in opposite directions with equal and opposite forces.

Answer: Option 1 — Both move away in opposite directions with equal and opposite forces
ByNewton's third law, the skaters push each other with equal and opposite forces and move apart in opposite directions → Option 1.
RRB Group D 2025-26 – 3 August 2026 Shift 1 · Newton's second law and momentum

Q35. When a net force acts on a body, what does Newton's second law predict will happen to the body?

  1. (a) The body will move at constant speed
  2. (b) The body will remain stationary
  3. (c) The body will always move in the opposite direction
  4. (d) The body will accelerate in the direction of the force
Answer & solution

Answer: (d) The body will accelerate in the direction of the force

Answer: Option 4 — The body will accelerate in the direction of the force
Newton's second law:F = ma. If a net (unbalanced) force acts, it produces an accelerationa = F/min thesame directionas the force. So the body accelerates along the force's direction → Option 4.
RRB Group D 2025-26 – 3 August 2026 Shift 2 · Newton's second law and momentum

Q36. If an object’s mass is doubled while the applied force remains constant, what happens to its acceleration according to the formula for force?

  1. (a) The acceleration remains unchanged
  2. (b) The acceleration becomes zero
  3. (c) The acceleration is halved
  4. (d) The acceleration is doubled
Answer & solution

Answer: (c) The acceleration is halved

Answer: Option 3 — The acceleration is halved
a = F/m (constant F). If massdoubles, a = F/(2m) =½of original → acceleration is halved → Option 3.
RRB NTPC UG CBT-1 2025-26 – 18 June 2026 Shift 3 · Numericals on force and momentum

Q37. If an object having a mass of 10 kg is moving with a velocity of 50 m/s, find the correct momentum of the object.

  1. (a) 40 kg m/s
  2. (b) 500 kg m/s
  3. (c) 5 kg m/s
  4. (d) 60 kg m/s
Answer & solution

Answer: (b) 500 kg m/s

Given: Mass (m) = 10 kg, Velocity (v) = 50 m/s
Formula:Momentum (p) = m × v
Momentum = 10 × 50 = 500 kg m/s
Answer: Option 2 → 500 kg m/s
RRB NTPC UG CBT-1 2025-26 – 14 June 2026 Shift 3 · Newton's third law and its applications

Q38. Action and reaction forces are exerted on which bodies during an interaction?

  1. (a) The same body
  2. (b) Only moving bodies
  3. (c) Only bodies at rest
  4. (d) Two different bodies
Answer & solution

Answer: (d) Two different bodies

Newton's Third Law of Motion
States: For every action, there is an equal and opposite reaction.
Key Point:Action and reaction forces always act ontwo different bodies.
Example: When you push a wall, you exert force on the wall (action), and the wall exerts equal force back on you (reaction).
The forces are equal in magnitude, opposite in direction, but act on different objects.
Answer: Option 4 → Two different bodies
SSC GD 2026 – 30 May 2026 Shift 2 · Friction

Q39. Why are the soles of shoes made grooved (with treads)?

  1. (a) To make them soft
  2. (b) To improve design
  3. (c) To provide better grip and safety
  4. (d) To reduce the weight of shoes
Answer & solution

Answer: (c) To provide better grip and safety

Correct Answer: To provide better grip and safety (Option 3)
The grooves (treads) on shoe soles are designed to increase friction between the shoe and the ground. The pattern of the grooves interlocks with surface irregularities, preventing slipping and providing better traction on wet, muddy, or uneven surfaces. This is a practical application of friction — the greater the contact and interlocking, the greater the grip.
Why others are wrong:
- To make them soft: Softness depends on the material used, not the groove pattern.
- To improve design: Grooves are functional, not primarily decorative.
- To reduce the weight of shoes: Grooves do not significantly affect the weight of shoes.
SSC GD 2026 – 29 May 2026 Shift 1 · Friction

Q40. Which of the following statement is NOT correct?

  1. (a) Sliding friction is smaller than static friction.
  2. (b) Friction depends on how hard the two surfaces press together.
  3. (c) Friction is important for many of our activities.
  4. (d) Friction can be decreased by making the surface rough.
Answer & solution

Answer: (d) Friction can be decreased by making the surface rough.

Correct Answer: Friction can be decreased by making the surface rough — Option (d)
The statement 'Friction can be decreased by making the surface rough' is NOT correct — making surfaces rough INCREASES friction. About Friction: Friction is a force that opposes the relative motion between two surfaces in contact; Types of friction: Static friction: Friction between surfaces when there is no relative motion (trying to start moving); highest value; Sliding friction (kinetic friction): Friction between surfaces when they slide against each other; less than static friction; Rolling friction: Friction when an object rolls on a surface; least among the three; Fluid friction: Friction in fluids (liquids and gases); Evaluation of each statement: Statement (a) — 'Sliding friction is smaller than static friction' — TRUE: Sliding friction (kinetic friction) is always LESS than static friction; this is why it's harder to start moving an object than to keep it moving once started; Statement (b) — 'Friction depends on how hard the two surfaces press together' — TRUE: Friction force = μ × Normal force (N); where μ is the coefficient of friction; the harder the surfaces press together (greater normal force), the greater the friction — this is TRUE; Statement (c) — 'Friction is important for many of our activities' — TRUE: Walking (friction between feet and ground), Writing (friction between pen and paper), Braking vehicles, Holding objects, Playing sports — all depend on friction; Statement (d) — 'Friction can be decreased by making the surface rough' — FALSE/INCORRECT: Making surfaces rough INCREASES friction; to DECREASE friction, surfaces should be made smooth, or lubrication should be used; Methods to decrease friction: Lubrication (oil, grease), Smooth surfaces, Ball bearings/rolling wheels, Streamlining (air resistance), Polishing.
Option (a) Sliding friction is smaller than static friction — Incorrect as an answer (statement is TRUE): Sliding friction (kinetic friction) IS smaller than static friction; this is a well-established physics principle; it's harder to START moving an object (overcome static friction) than to KEEP it moving (kinetic friction); this statement is TRUE and NOT the incorrect one.
Option (b) Friction depends on how hard the two surfaces press together — Incorrect as an answer (statement is TRUE): Friction DOES depend on the normal force (how hard the surfaces press together); F = μN (friction = coefficient × normal force); greater the normal force, greater the friction; this is TRUE and NOT the incorrect one.
Option (c) Friction is important for many of our activities — Incorrect as an answer (statement is TRUE): Friction IS important for many activities — walking, writing, driving, sports, gripping objects; without friction we couldn't walk or hold anything; this statement is TRUE and NOT the incorrect one.
SSC GD 2026 – 29 May 2026 Shift 3 · Newton's third law and its applications

Q41. Why do action and reaction forces, though equal in magnitude, not always produce equal accelerations?

  1. (a) The forces act on the same object
  2. (b) The forces are in the same direction
  3. (c) The objects have different masses
  4. (d) One force is stronger than the other
Answer & solution

Answer: (c) The objects have different masses

Correct Answer: The objects have different masses — Option (c)
Action and reaction forces produce unequal accelerations because the objects they act on have different masses. About Newton's Third Law: Statement: For every action, there is an equal and opposite reaction; Key feature: Action and reaction forces are: Equal in magnitude, Opposite in direction, Act on DIFFERENT objects (this is crucial); Example: When you push a wall: Action: You push the wall (force on wall); Reaction: Wall pushes back on you (force on you); Both forces are equal and opposite; BUT accelerations are different because masses are different; Mathematical explanation: Newton's Second Law: F = ma → a = F/m; If same force F acts on object 1 (mass m₁) and object 2 (mass m₂): Acceleration of object 1: a₁ = F/m₁; Acceleration of object 2: a₂ = F/m₂; If m₁ ≠ m₂, then a₁ ≠ a₂; Classic example — Gun firing a bullet: Action: Gun pushes bullet forward; Reaction: Bullet pushes gun backward (recoil); Same force in magnitude — but bullet (very small mass) gets HUGE acceleration; Gun (large mass) gets small acceleration (recoil); a_bullet = F/ m_bullet >> a_gun = F/ m_gun (because m_gun >> m_bullet ); Example — Person jumping from a boat: Action: Person pushes backward on boat; Reaction: Boat pushes person forward; Person accelerates forward; Boat moves backward but with much less acceleration (because boat is heavier); Why the other options are wrong: Forces acting on SAME object (a) — FALSE: they act on different objects; Forces in SAME direction (b) — FALSE: they are OPPOSITE in direction; One force stronger (d) — FALSE: they are EQUAL in magnitude.
Option (a) The forces act on the same object — Incorrect: This is fundamentally wrong — action and reaction forces do NOT act on the same object; they act on DIFFERENT objects; if they acted on the same object, they would cancel each other and result in zero net force and zero acceleration; Newton's Third Law explicitly states that action and reaction are on different bodies.
Option (b) The forces are in the same direction — Incorrect: Action and reaction forces are NOT in the same direction — they are OPPOSITE in direction (Newton's Third Law: equal and opposite reaction); if they were in the same direction, the net effect on a system would be doubled force, not zero; the correct reason for unequal accelerations is that the objects have different masses.
Option (d) One force is stronger than the other — Incorrect: By Newton's Third Law, action and reaction forces are EQUAL in magnitude — neither is stronger than the other; the forces are equal and opposite; the reason for unequal accelerations is NOT that one force is stronger, but that the objects on which these equal forces act have DIFFERENT masses (F = ma, so a = F/m).
SSC GD 2026 – 26 May 2026 Shift 1 · Newton's first law and inertia

Q42. What does the mass of an object measure?

  1. (a) Its weight
  2. (b) Its inertia
  3. (c) Its volume
  4. (d) Its density
Answer & solution

Answer: (b) Its inertia

Correct Answer: Its inertia — Option (b)
The mass of an object is a measure of its inertia — the resistance of an object to changes in its state of motion. About Mass and Inertia: Mass: A fundamental property of matter; it measures the quantity of matter in an object; SI unit: kilogram (kg); Mass is a scalar quantity; Mass remains constant everywhere (on Earth, Moon, or space); Inertia: The tendency of an object to resist changes in its state of rest or motion; Newton's First Law of Motion (Law of Inertia) states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an external force; Mass is the measure of inertia: Greater the mass → Greater the inertia → More force needed to change its state; A heavier truck has more inertia than a bicycle — it is harder to start or stop; Newton's Second Law: F = ma; Here 'm' is the measure of inertia (resistance to acceleration); Important distinctions: Mass vs Weight: Mass = amount of matter (kg); Weight = gravitational force on mass (W = mg); Weight varies with gravity but mass remains constant; Mass vs Volume: Volume is the amount of space occupied; mass is the amount of matter; Mass vs Density: Density = mass/volume; density is mass per unit volume, not what mass measures; Examples: A cricket ball and a tennis ball of same size have different masses — the heavier cricket ball has more inertia and requires more force to accelerate.
Option (a) Its weight — Incorrect: Weight is the gravitational force acting on an object (W = mg) — weight depends on gravity and varies with location; mass is NOT a measure of weight; mass measures inertia, while weight is the gravitational force on mass.
Option (c) Its volume — Incorrect: Volume is the amount of three-dimensional space occupied by an object — it is a completely different physical quantity from mass; mass does NOT measure volume; it measures the quantity of matter and inertia.
Option (d) Its density — Incorrect: Density is mass per unit volume (ρ = m/V) — it is a derived quantity combining both mass and volume; mass does NOT measure density; mass measures inertia (resistance to change in motion). The candidate selected this incorrect option.
RRB NTPC UG CBT-1 2025-26 – 9 May 2026 Shift 1 · Numericals on force and momentum

Q43. What will be the resultant force if a body of mass 10 kg is moving with an acceleration of 5m/sec²?

  1. (a) 5 Newton
  2. (b) 2 Newton
  3. (c) 50 Newton
  4. (d) 2 Joule
Answer & solution

Answer: (c) 50 Newton

Given: Mass (m) = 10 kg, Acceleration (a) = 5 m/s²
Formula:Force (F) = Mass × Acceleration
F = m × a = 10 × 5 =50 N
Answer: Option 3 → 50 Newton
RRB NTPC UG CBT-1 2025-26 – 7 May 2026 Shift 2 · Friction

Q44. When a book is pushed across a table surface, which type of friction mainly opposes its motion?

  1. (a) Rolling friction
  2. (b) Sliding friction
  3. (c) Fluid friction
  4. (d) Magnetic friction
Answer & solution

Answer: (b) Sliding friction

Topic: Types of Friction
When a book is pushed across a table, the surfaces in contact slide over each other.
Sliding friction(also called kinetic friction) acts between two surfaces that are sliding relative to each other.
Rolling friction occurs when objects roll (like wheels).
Fluid friction acts in liquids/gases.
Magnetic friction is not a standard friction type.
Answer: Option 2 → Sliding friction
SSC GD 2026 – 4 May 2026 Shift 2 · Newton's first law and inertia

Q45. According to Newton's First Law, an object remains at rest or in uniform motion until:

  1. (a) Balanced forces act on it
  2. (b) Gravity changes its motion
  3. (c) An applied force compels a change
  4. (d) Friction is removed
Answer & solution

Answer: (c) An applied force compels a change

Correct Answer: An applied force compels a change — Option (c)
Newton's First Law of Motion (Law of Inertia) states that an object at rest stays at rest, and an object in uniform motion continues in that motion, unless acted upon by an external unbalanced (net) force that compels a change. This is the principle of inertia — objects resist changes to their state of motion.
Option (a) Balanced forces act on it — Incorrect: Balanced (equal and opposite) forces result in no net force, so the object continues in its current state — no change is forced. This is consistent with Newton's First Law, not a violation of it.
Option (b) Gravity changes its motion — Incorrect: Gravity is a force, but under Newton's First Law, it is only when an unbalanced net force acts that motion changes.
Option (d) Friction is removed — Incorrect: Friction's removal is not what keeps an object in motion; in an ideal frictionless environment, uniform motion continues by inertia.
RRB NTPC GL CBT-1 2025-26 – 25 March 2026 Shift 3 · Newton's first law and inertia

Q46. Which of the following best describes the tendency of undisturbed objects to remain at rest or to keep moving with the same velocity?

  1. (a) Momentum
  2. (b) Acceleration
  3. (c) Force
  4. (d) Inertia
Answer & solution

Answer: (d) Inertia

Newton's First Law of Motion
An object at rest stays at rest, and an object in motion continues in motion with the same velocity unless acted upon by an external force.
This property of matter to resist change in its state of rest or uniform motion is calledInertia.
Momentum = mass × velocity (quantity of motion)
Acceleration = rate of change of velocity
Force = cause of change in motion
Inertia = resistance to change in motion
Answer: Option 4 → Inertia
RRB NTPC GL CBT-1 2025-26 – 22 March 2026 Shift 1 · Newton's second law and momentum

Q47. Momentum of an object is defined as the product of its mass and velocity, hence what are its SI units?

  1. (a) kg m s
  2. (b) g m s^(–1)
  3. (c) kg m s^(–1)
  4. (d) kg m s^(–2)
Answer & solution

Answer: (c) kg m s^(–1)

Momentum = Mass × Velocity
SI unit of Mass = kg
SI unit of Velocity = m/s = m s⁻¹
SI unit of Momentum = kg × m s⁻¹ =kg m s⁻¹
Answer: Option 3 → kg m s⁻¹
RRB NTPC GL CBT-1 2025-26 – 18 March 2026 Shift 3 · Newton's first law and inertia

Q48. When a motorcar makes a sharp turn at high speed, we tend to get thrown to one side. Which of the following explains this phenomenon?

  1. (a) Change in air pressure inside the car pushes us outwards.
  2. (b) The law of inertia causes our body to resist the change in direction.
  3. (c) The friction between the road and the tires decreases.
  4. (d) The force of gravity acts in the opposite direction.
Answer & solution

Answer: (b) The law of inertia causes our body to resist the change in direction.

When car turns sharply, it changes direction due to centripetal force from road friction.
Our body tends to continue in straight-line motion due toinertia.
Body resists the change in direction → appears to be thrown outward.
This isnot a real outward force, but effect of inertia in non-inertial frame.
Answer: Option 2 → The law of inertia causes our body to resist the change in direction.
RRB Technician Grade III 2025-26 – 10 March 2026 Shift 3 · Newton's third law and its applications

Q49. Even though action and reaction forces are equal in size, they may not cause equal accelerations. Why?

  1. (a) Because the forces act on the same object
  2. (b) Because reaction forces are always weaker in effect
  3. (c) Because only the larger force causes acceleration
  4. (d) Because each force acts on a different object, and the objects may have different masses
Answer & solution

Answer: (d) Because each force acts on a different object, and the objects may have different masses

Action and reaction forces are equal in magnitude but act on two different objects according to Newton's third law.
Acceleration depends on the net force acting on an object and the object's mass (Newton's second law: F = ma).
Since action and reaction forces act on different objects, they may have different masses.
Because acceleration (a) = Force (F) / Mass (m), the accelerations of the objects can differ even if forces are equal.
Hence, equal forces acting on different objects do not produce equal accelerations if the masses differ.
RRB Technician Grade III 2025-26 – 10 March 2026 Shift 3 · Newton's third law and its applications

Q50. Which of the following is/are NOT true about action reaction forces?
(i) Action reaction forces are unequal in magnitude and always act in the same direction.
(ii) Action reaction forces act on different bodies.
(iii) Action reaction forces act on the same body.

  1. (a) Only (iii)
  2. (b) Only (ii)
  3. (c) Both (i) and (iii)
  4. (d) Both (i) and (ii)
Answer & solution

Answer: (c) Both (i) and (iii)

Correct option: 3
Action and reaction forces are equal in magnitude and opposite in direction, so statement (i) is false.
Statement (ii) is true because action and reaction forces act on different bodies.
Statement (iii) is false because action and reaction forces do not act on the same body.
Hence, both (i) and (iii) are NOT true about action reaction forces.
This aligns with Newton's third law of motion.
RRB Technician Grade III 2025-26 – 9 March 2026 Shift 2 · Numericals on force and momentum

Q51. A wooden block of mass 50 kg is placed on a smooth horizontal surface. A constant horizontal force of 'X' N is applied on it while it is at rest. The block acquires a velocity of 10 m/s in 2 s. What is the value of X?

  1. (a) 10 N
  2. (b) 100 N
  3. (c) 25 N
  4. (d) 250 N
Answer & solution

Answer: (d) 250 N

Given, mass m = 50 kg
Initial velocity u = 0 (at rest)
Final velocity v = (10 m)/(s)
Time t = 2 s
Acceleration a = ((v - u))/(t)
a = ((10 - 0))/(2) = (5 m)/(s²)
Force F = mass × acceleration
F = 50 × 5 = 250 N
Hence, the required constant force X = 250 N
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 2 · Numericals on force and momentum

Q52. A car of mass 1000 kg moving with a velocity of 20 m/s comes to rest in 10 s after applying the brakes. What is the value of the force applied by the brakes?

  1. (a) - 2000 N
  2. (b) - 5000 N
  3. (c) - 500 N
  4. (d) - 200 N
Answer & solution

Answer: (a) - 2000 N

Given: mass (m) = 1000 kg, initial velocity (u) = 20 m/s, final velocity (v) = 0 m/s, time (t) = 10 s.
We need to find the braking force (F).
First, calculate acceleration (a) using formula: a = (v − u) / t
a = (0 − 20) / 10 = -2 m/s² (negative sign indicates deceleration).
Use Newton's second law: F = m × a
F = 1000 × (-2) = -2000 N
Force of 2000 N acts opposite to motion to bring the car to rest.
Magnitude of force applied by brakes = - 2000 N.
Final answer: Option 1
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 3 · Numericals on force and momentum

Q53. An unbalanced force of 100 N acts on a body at rest such that it acquires a velocity of 5 m/s in 10 s. How much is the mass of the body?

  1. (a) 2 kg
  2. (b) 50 kg
  3. (c) 5 kg
  4. (d) 200 kg
Answer & solution

Answer: (d) 200 kg

Force (F) = 100 N
Initial velocity (u) = 0 m/s (body at rest)
Final velocity (v) = 5 m/s
Time (t) = 10 s
Acceleration (a) = (v − u) / t = (5 − 0) / 10 = 0.5 m/s²
From Newton's second law, F = m × a
Therefore, m = F / a = 100 / 0.5 = 200 kg
The correct mass of the body is 200 kg
Final answer: Option 2
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 2 · Newton's first law and inertia

Q54. Newton’s first law of motion explains the concept of _________.

  1. (a) Change in momentum
  2. (b) Continuous acceleration
  3. (c) Balanced forces
  4. (d) Net force being non-zero
Answer & solution

Answer: (c) Balanced forces

Newton’s first law of motion states that an object remains at rest or in uniform motion unless acted upon by a net external force.
This means the forces on the object are balanced, resulting in no change in motion.
Hence, the law explains the concept of balanced forces.
Correct option is Option 3.
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 3 · Force, its effects and types

Q55. Unbalanced forces acting on an object always cause _________.

  1. (a) No change in motion
  2. (b) Increase in mass
  3. (c) Object to remain at rest
  4. (d) Change in motion
Answer & solution

Answer: (d) Change in motion

Unbalanced forces on an object cause a net force to act on it.
According to Newton's first law, no change in motion occurs if forces are balanced.
If forces are unbalanced, the object accelerates or changes its velocity.
This means the object's motion changes.
Hence, unbalanced forces always cause a change in motion.
Final answer: Option 4
RRB JE CBT-1 2025-26 – 25 February 2026 Shift 3 · Newton's first law and inertia

Q56. A car suddenly changes direction while moving at constant speed. Which aspect of inertia is being demonstrated, and how does the car’s mass influence this effect?

  1. (a) The inertia of speed is demonstrated, and a lighter car resists direction change more.
  2. (b) The inertia of rest is demonstrated, and the car’s mass does not affect direction changes.
  3. (c) Mass only affects speed, not direction, when a car turns.
  4. (d) The inertia of direction is demonstrated, and a car with greater mass will resist the change in direction more.
Answer & solution

Answer: (d) The inertia of direction is demonstrated, and a car with greater mass will resist the change in direction more.

Correct option is 4.
When a car suddenly changes direction, it demonstrates the inertia of direction (a component of inertia related to change in velocity vector).
Inertia resists change in motion direction, not just speed or rest.
A car with greater mass has more inertia, so it resists changes in direction more strongly.
Thus, the heavier the car, the harder it is to change its direction abruptly.
Final answer: Option 4
RRB JE CBT-1 2025-26 – 25 February 2026 Shift 3 · Newton's third law and its applications

Q57. Which of the following situations is NOT an example of action and reaction forces?

  1. (a) A swimmer pushing water backwards
  2. (b) A bat hitting a cricket ball
  3. (c) A ball thrown upward comes back down due to the pull of gravity.
  4. (d) A rocket launching upwards
Answer & solution

Answer: (c) A ball thrown upward comes back down due to the pull of gravity.

Option 3 is correct because the ball coming down due to gravity is not an action-reaction pair.
It is a single force acting on the ball (gravity).
Action and reaction forces always act in pairs on two different bodies, equal in magnitude and opposite in direction.
Examples:
1. Swimmer pushes water backwards (action), water pushes swimmer forward (reaction).
2. Bat hits ball (action), ball exerts equal opposite force on bat (reaction).
4. Rocket expels gas downwards (action), gas pushes rocket upwards (reaction).
Thus, option 3 is NOT an example of action and reaction forces.
Final answer: Option 3
RRB JE CBT-1 2025-26 – 20 February 2026 Shift 3 · Newton's first law and inertia

Q58. A passenger in a moving car feels a jerk backward when the car suddenly starts. How does the first law of motion explain this experience?

  1. (a) The passenger tends to remain at rest while the car moves forward, showing inertia.
  2. (b) The passenger is pushed backward by the air inside the car.
  3. (c) The seat pushes the passenger forward, causing the sensation.
  4. (d) Friction from the seat creates the backward jerk.
Answer & solution

Answer: (a) The passenger tends to remain at rest while the car moves forward, showing inertia.

According to Newton's first law, an object at rest tends to stay at rest unless acted upon by an external force.
When the car suddenly starts moving forward, the passenger's body tends to remain at rest due to inertia.
This causes the passenger to feel a backward jerk as their body resists the forward motion of the car.
Hence, the backward jerk is explained by inertia keeping the passenger at rest while the car moves forward.
Final answer: Option 1
RRB JE CBT-1 2025-26 – 20 February 2026 Shift 1 · Centripetal and centrifugal force

Q59. Suppose a student wants to design an amusement park ride that moves people in a circle at uniform speed. Which concept should the student apply to ensure riders stay safely in their seats during the circular motion?

  1. (a) Increasing speed randomly will keep them safe
  2. (b) A constant outward force is needed to keep riders pressed against their seats
  3. (c) A constant inward (centripetal) force is needed on the riders to keep them in uniform circular motion
  4. (d) Gravity alone is sufficient to keep the riders in place
Answer & solution

Answer: (c) A constant inward (centripetal) force is needed on the riders to keep them in uniform circular motion

Correct option is 3
To keep riders safely in their seats during circular motion, a constant inward force (centripetal force) is required.
This inward force acts towards the centre of the circle and maintains uniform circular motion.
It prevents riders from flying outward due to inertia.
Therefore, the ride must provide centripetal force to keep riders moving in a circle safely.
Options 1, 2 and 4 are incorrect because:
1 is unsafe as randomly increasing speed does not provide controlled force.
2 is wrong because the force is inward, not outward.
4 is incorrect as gravity alone cannot provide the necessary centripetal force.
This is a fundamental principle in circular motion in physics.
Answer is Option 3.
SSC MTS 2025 – 19 February 2026 Shift 1 · Force, its effects and types

Q60. For force to come into play at least _____ objects must interact.

  1. (a) 2
  2. (b) 3
  3. (c) 4
  4. (d) 5
Answer & solution

Answer: (a) 2

The correct answer is option 1.
Force is an interaction between two objects — it is the push or pull that one object exerts on another. For a force to exist, there must be at least two objects interacting. A single isolated object cannot experience a net external force. This is a fundamental concept in Newton's laws of motion.
Option 2 is incorrect: Three objects are not the minimum required for force to come into play.
Option 3 is incorrect: Four objects are not the minimum required.
Option 5 is incorrect: Five objects are not the minimum required.
SSC MTS 2025 – 19 February 2026 Shift 2 · Numericals on force and momentum

Q61. A constant force acts on an object of mass 6 kg for a duration of 5 seconds. It increases the object's velocity from 3 m/s to 8 m/s. Find the magnitude of the applied force.

  1. (a) 6 N
  2. (b) 10 N
  3. (c) 15 N
  4. (d) 20 N
Answer & solution

Answer: (a) 6 N

The correct answer is option 1.
Using Newton's Second Law: F = ma
First, find acceleration: a = (v - u) / t = (8 - 3) / 5 = 5 / 5 = 1 m/s²
Then, find force: F = m × a = 6 kg × 1 m/s² = 6 N
Option 2 is incorrect: 10 N would require an acceleration of 10/6 ≈ 1.67 m/s², which does not match the given data.
Option 3 is incorrect: 15 N would require an acceleration of 15/6 = 2.5 m/s², which does not match.
Option 4 is incorrect: 20 N would require an acceleration of 20/6 ≈ 3.33 m/s², which does not match the given data.
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 2 · Numericals on force and momentum

Q62. An object of mass 3 kg initially at rest is subjected to a constant force of 9 N for 2 seconds. What will be its final velocity?

  1. (a) 6 m/s
  2. (b) 9 m/s
  3. (c) 18 m/s
  4. (d) 3 m/s
Answer & solution

Answer: (a) 6 m/s

Force (F) = 9 N
Mass (m) = 3 kg
Time (t) = 2 s
Initial velocity (u) = 0 (object initially at rest)
Acceleration (a) = (Force)/(Mass) = (9)/(3) = 3m/s^(2)
Final velocity (v) = u + at = 0 + 3 × 2 = 6m/s
Final answer: Option 1
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 2 · Newton's second law and momentum

Q63. If a constant force acts on two objects of different masses, which statement best describes their acceleration according to the second law of motion?

  1. (a) The object with greater mass will have greater acceleration.
  2. (b) Acceleration does not depend on mass.
  3. (c) The object with smaller mass will have greater acceleration.
  4. (d) Both objects will have the same acceleration.
Answer & solution

Answer: (c) The object with smaller mass will have greater acceleration.

According to Newton's second law of motion, Force = mass × acceleration (F = m × a).
For the same constant force, acceleration = Force / mass.
Therefore, the object with smaller mass will have greater acceleration because acceleration is inversely proportional to mass when force is constant.
Hence, option 3 is correct.
Final answer: Option 3
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 1 · Newton's third law and its applications

Q64. When a gun is fired, it recoils backward as the bullet moves forward. How does this demonstrate Newton’s third law of motion?

  1. (a) The gun recoils because the bullet moves faster than the gun.
  2. (b) The bullet moves forward only because the gun has stored energy.
  3. (c) The gun pushes the bullet forward, and the bullet pushes the gun backward with an equal and opposite force.
  4. (d) The gun moves backward because it is heavier than the bullet.
Answer & solution

Answer: (c) The gun pushes the bullet forward, and the bullet pushes the gun backward with an equal and opposite force.

When a gun is fired, it exerts a force on the bullet, pushing it forward.
According to Newton’s third law, for every action, there is an equal and opposite reaction.
Thus, as the gun pushes the bullet forward, the bullet pushes the gun backward with equal force.
This backward movement of the gun is called recoil and directly demonstrates Newton’s third law of motion.
Hence, the forces between the gun and the bullet are equal in magnitude and opposite in direction.
Final answer: Option 3
SSC MTS 2025 – 18 February 2026 Shift 3 · Newton's first law and inertia

Q65. What is the first law of motion also known as?

  1. (a) Law of acceleration
  2. (b) Law of action and reaction
  3. (c) Law of momentum
  4. (d) Law of inertia
Answer & solution

Answer: (d) Law of inertia

The correct answer is option 4.
Newton's First Law of Motion states that an object at rest stays at rest, and an object in motion stays in motion at constant velocity, unless acted upon by an external force. This property of matter — its tendency to resist changes in its state of motion — is called inertia. Hence, Newton's First Law is also known as the Law of Inertia.
Option 1 is incorrect: Law of acceleration refers to Newton's Second Law (F = ma), which describes how force causes acceleration.
Option 2 is incorrect: Law of action and reaction refers to Newton's Third Law — for every action there is an equal and opposite reaction.
Option 3 is incorrect: Law of momentum is associated with Newton's Second Law (force equals rate of change of momentum); it is not the name of the First Law.
SSC MTS 2025 – 17 February 2026 Shift 3 · Friction

Q66. Which of the following statement is NOT correct regarding friction?

  1. (a) The force required to overcome friction at the instant an object starts moving from rest is a measure of static friction.
  2. (b) The force required to keep the object moving with the same speed is a measure of sliding friction.
  3. (c) When one body rolls over the surface of another body, the resistance to its motion is called rolling friction.
  4. (d) Rolling increases the friction and hence the rolling friction is more than the sliding friction.
Answer & solution

Answer: (d) Rolling increases the friction and hence the rolling friction is more than the sliding friction.

Option 4 is NOT correct. Rolling friction is actually LESS than sliding friction — that is why wheels (rolling) are preferred over dragging (sliding) to move objects. Rolling reduces friction. Options 1, 2, and 3 are all correct statements about the different types of friction.
SSC MTS 2025 – 13 February 2026 Shift 3 · Friction

Q67. What is the direction of the force of friction in relation to the motion of an object?

  1. (a) In the same direction
  2. (b) Perpendicular to the direction of motion
  3. (c) Randomly directed
  4. (d) Always opposite to the direction of motion
Answer & solution

Answer: (d) Always opposite to the direction of motion

Friction is a resistive force that acts on a moving object and always opposes the relative motion between two surfaces in contact. By Newton's laws, friction acts in the direction exactly opposite to the direction of motion of the object, thereby slowing it down.
Why other options are incorrect:
- In the same direction: Friction opposes motion; it never acts in the same direction as motion.
- Perpendicular to the direction of motion: Normal force acts perpendicular to the surface; friction acts along the surface, opposing motion.
- Randomly directed: Friction follows a definite direction — always opposing motion; it is not random.
SSC MTS 2025 – 12 February 2026 Shift 1 · Force, its effects and types

Q68. Which of the following is an example of non-contact force?
I. Magnetic force
II. Gravitational force

  1. (a) Only I
  2. (b) Only II
  3. (c) Both I and II
  4. (d) Neither I nor II
Answer & solution

Answer: (c) Both I and II

Correct Answer: Option 3 – Both I and II
Non-contact forces act between objects without physical contact.
Statement I: Magnetic force is a non-contact force — a magnet attracts iron objects from a distance without touching them.
Statement II: Gravitational force is a non-contact force — the Earth pulls objects towards it without direct contact.
Both magnetic force and gravitational force are classic examples of non-contact forces. Other examples include electrostatic force.
Why 'Only I' or 'Only II' are wrong: Both forces are non-contact in nature, so selecting only one is incorrect.
SSC MTS 2025 – 12 February 2026 Shift 3 · Friction

Q69. Which of the following is correct regarding fluid friction?
I. When objects move through fluids they lose energy due to it.
II. It can be minimised by giving suitable shapes to bodies moving in fluids.

  1. (a) Only I
  2. (b) Only II
  3. (c) Both I and II
  4. (d) Neither I nor II
Answer & solution

Answer: (c) Both I and II

Correct Answer: Option 3 – Both I and II
Statement I is correct: Fluid friction (drag) opposes the motion of objects moving through fluids (liquids or gases). Objects lose energy due to this friction, which is why energy must be continuously supplied to maintain motion through a fluid.
Statement II is correct: Fluid friction can be minimised by giving streamlined (aerodynamic or hydrodynamic) shapes to objects. This is why ships, aircraft, and fish have tapered shapes — to reduce the drag force and energy loss while moving through fluids.
Both statements are correct, so the answer is Both I and II.
SSC MTS 2025 – 10 February 2026 Shift 3 · Newton's third law and its applications

Q70. The recoil experienced when firing a bullet from a gun is an example of _____.

  1. (a) Newton's second law of motion
  2. (b) Newton's law of gravitation
  3. (c) Newton's third law of motion
  4. (d) Newton's first law of motion
Answer & solution

Answer: (c) Newton's third law of motion

The correct answer is Newton's third law of motion (Option 3). Newton's third law states: 'For every action, there is an equal and opposite reaction.' When a bullet is fired forward, the gun experiences an equal and opposite force backward — this is the recoil. Option 1 (Second law: F=ma) relates to force and acceleration, not recoil. Option 2 (Law of Gravitation) relates to gravitational force between masses. Option 4 (First law: law of inertia) relates to objects remaining at rest or in uniform motion unless acted upon.
SSC MTS 2025 – 5 February 2026 Shift 1 · Friction

Q71. What is the frictional force exerted by fluids known as?

  1. (a) Lift
  2. (b) Drag
  3. (c) Pressure
  4. (d) Load
Answer & solution

Answer: (b) Drag

Correct Answer: Drag
Drag is the frictional force exerted by fluids (liquids and gases) on objects moving through them. It acts opposite to the direction of motion and is also called fluid friction or viscous drag. It affects the speed of vehicles, aircraft, and ships.
Why other options are wrong:
Lift - The upward force on an object due to fluid flow (e.g., wings of an aircraft), not friction.
Pressure - Force per unit area exerted by fluid on surfaces; not specifically friction.
Load - The weight or external force on a structure; unrelated to fluid friction.
SSC Stenographer 2025 – 7 December 2025 Shift 2 · Impulse

Q72. Why does a skilled cricketer move his hands backwards while catching a fast-moving ball?

  1. (a) To increase the speed of the ball during impact.
  2. (b) To apply a greater opposing force on the ball for a quick stop.
  3. (c) To reduce the force by increasing the time over which momentum changes.
  4. (d) To decrease the weight of the ball using gravity.
Answer & solution

Answer: (c) To reduce the force by increasing the time over which momentum changes.

When a cricketer catches a fast-moving ball, the ball has high momentum. If the hands are kept stiff, the momentum changes suddenly, producing a large force which can hurt the hands. By moving the hands backwards, the time taken to stop the ball increases. Since Force = Change in Momentum / Time , increasing the time reduces the force. Hence, the impact on the hands becomes less painful.
SSC CHSL Tier-1 2025 – 25 November 2025 Shift 3 · Newton's first law and inertia

Q73. What is inertia?

  1. (a) The ability of an object to change its velocity
  2. (b) The tendency of an object to resist any change in its state of motion
  3. (c) The force applied by an engine to move a vehicle
  4. (d) The force that pulls an object towards the Earth
Answer & solution

Answer: (b) The tendency of an object to resist any change in its state of motion

Inertia is the tendency of an object to resist any change in its state of motion. It is a fundamental property of matter. According to Newton's First Law of Motion, an object at rest stays at rest and an object in motion stays in motion unless acted upon by an external force — this is the principle of inertia.
Option 1 (ability to change velocity) contradicts inertia; Option 3 describes engine force; Option 4 describes gravity. Hence, Option 2 is correct.
SSC CHSL Tier-1 2025 – 22 November 2025 Shift 2 · Friction

Q74. What is a disadvantage of friction?

  1. (a) It increases speed
  2. (b) It improves machinery efficiency
  3. (c) It prevents objects from wearing out
  4. (d) It causes wear and tear of materials
Answer & solution

Answer: (d) It causes wear and tear of materials

The primary disadvantage of friction is that it causes wear and tear of materials. When surfaces rub against each other, friction gradually degrades them and reduces the lifespan of machinery parts.
Options 1, 2, and 3 are wrong: friction does not increase speed; it actually reduces efficiency (energy is lost as heat); and friction causes wear, not prevents it.
SSC CHSL Tier-1 2025 – 21 November 2025 Shift 3 · Force, its effects and types

Q75. Which of the following statements is correct regarding force?
I. If an unbalanced force is applied on an object, there will be a change either in its speed or in the direction of its motion.
II. To accelerate the motion of an object, a balanced force is required.

  1. (a) 1. Only I
  2. (b) 2. Only II
  3. (c) 3. Both I and II
  4. (d) 4. Neither I nor II
Answer & solution

Answer: (a) 1. Only I

Statement I is correct: An unbalanced (net) force acting on an object causes a change in its speed or direction of motion, as per Newton's Second Law of Motion. Statement II is incorrect: To accelerate an object, an UNBALANCED force is required. Balanced forces (equal and opposite) result in no change in motion — the object remains in equilibrium. Hence only Statement I is correct.
SSC CHSL Tier-1 2025 – 20 November 2025 Shift 2 · Friction

Q76. Which of the following statement is correct regarding fluid friction?
I. It is also called a drag.
II. It depends on the speed of the object with respect to the fluid.

  1. (a) Only I
  2. (b) Only II
  3. (c) Both I and II
  4. (d) Neither I nor II
Answer & solution

Answer: (c) Both I and II

Correct Answer: Both I and II
Statement I: Fluid friction is also called drag - CORRECT. When an object moves through a fluid (liquid or gas), the resistance it encounters is called fluid friction or drag. Examples include air drag on aeroplanes and water resistance on ships.
Statement II: Fluid friction depends on the speed of the object relative to the fluid - CORRECT. The drag force increases with the speed of the object. At higher speeds, a greater friction force acts on the object. This is why aeroplanes experience more drag at higher speeds.
Both statements accurately describe fluid friction.
Why 'Only I', 'Only II', and 'Neither' are wrong: Both statements are correct.
SSC CHSL Tier-1 2025 – 19 November 2025 Shift 1 · Newton's third law and its applications

Q77. The operation of a satellite launch vehicle is based on which of the following?

  1. (a) Newton's first law of motion
  2. (b) Newton's second law of motion
  3. (c) Newton's third law of motion
  4. (d) Archimede's principle
Answer & solution

Answer: (c) Newton's third law of motion

Correct Answer: Newton's third law of motion
The operation of a satellite launch vehicle (rocket) is based on Newton's Third Law of Motion: 'For every action, there is an equal and opposite reaction.' In a rocket, hot gases are expelled downward (action) at high speed, which creates an equal and opposite reaction force that propels the rocket upward (reaction). This is the principle of rocket propulsion.
Why other options are wrong:
- Newton's first law (Law of Inertia): An object at rest stays at rest unless acted upon by a net force; describes inertia, not rocket propulsion.
- Newton's second law (F = ma): Relates force, mass, and acceleration; while relevant to rocket dynamics, it is not the fundamental operating principle.
- Archimedes' principle: Relates to buoyancy of objects in fluids; not applicable to rocket operation.
SSC CHSL Tier-1 2025 – 15 November 2025 Shift 3 · Newton's first law and inertia

Q78. The statement given below signifies which law/principle: 'An object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied force.'

  1. (a) First law of motion
  2. (b) Second law of motion
  3. (c) Third law of motion
  4. (d) Bernoulli's principle
Answer & solution

Answer: (a) First law of motion

The given statement is the definition of Newton's First Law of Motion, also known as the Law of Inertia. It states that a body remains in its state of rest or uniform motion unless acted upon by an external unbalanced force. Option 2 (Second law) relates to force = mass × acceleration (F = ma). Option 3 (Third law) relates to action and reaction forces. Option 4 (Bernoulli's principle) relates to fluid dynamics and pressure.
SSC CHSL Tier-1 2025 – 14 November 2025 Shift 2 · Force, its effects and types

Q79. Which of the following statement is an example of contact force?
I. Electrostatic force
II. Friction

  1. (a) Only I
  2. (b) Only II
  3. (c) Both I and II
  4. (d) Neither I nor II
Answer & solution

Answer: (b) Only II

Statement I - Electrostatic force: This is a non-contact force. It acts at a distance between charged objects without physical contact. Statement II - Friction: This is a contact force. It acts between two surfaces in contact and opposes relative motion. Therefore, Only II (Friction) is an example of contact force.
SSC CHSL Tier-1 2025 – 14 November 2025 Shift 2 · Newton's second law and momentum

Q80. What is the formula for calculating the momentum of an object? (p = momentum, m = mass, a = acceleration, v = velocity)

  1. (a) p = m/a
  2. (b) p = ma
  3. (c) p = mv
  4. (d) p = m/v
Answer & solution

Answer: (c) p = mv

Momentum is defined as the product of mass and velocity of an object: Momentum (p) = Mass (m) x Velocity (v) SI unit of momentum is kg.m /s. Why others are wrong: - p = m/a: This has no standard physical meaning. - p = ma: This is the formula for Force (F = ma), not momentum. - p = m/v: This is an incorrect formula; dividing mass by velocity does not give momentum.
SSC CHSL Tier-1 2025 – 13 November 2025 Shift 3 · Force, its effects and types

Q81. What does a change in either the speed or direction of an object signify?

  1. (a) A change in its mass
  2. (b) A change in its state of motion
  3. (c) A change in its shape
  4. (d) A change in its temperature
Answer & solution

Answer: (b) A change in its state of motion

According to Newton's First Law of Motion, any change in the speed or direction of an object constitutes a change in its state of motion. Such a change requires a net external force. Mass remains constant regardless of speed or direction changes; shape and temperature are independent of the object's motion state.
SSC CHSL Tier-1 2025 – 13 November 2025 Shift 2 · Newton's third law and its applications

Q82. Newton's third law of motion states that ___.

  1. (a) For every action, there is an equal and opposite reaction
  2. (b) For every action, the reaction is opposite but greater in magnitude
  3. (c) The rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of force
  4. (d) An object in motion remains in motion unless acted upon by a force
Answer & solution

Answer: (a) For every action, there is an equal and opposite reaction

Newton's Third Law of Motion states: 'For every action, there is an equal and opposite reaction.' This means that whenever one body exerts a force on another, the second body exerts a force of the same magnitude but in the opposite direction on the first body. Why others are wrong: - Option : The reaction is equal (not greater) in magnitude. - Option : This describes Newton's Second Law of Motion. - Option : This describes Newton's First Law of Motion (Law of Inertia).
SSC CGL Tier-1 2025 – 20 September 2025 Shift 2 · Newton's third law and its applications

Q83. Why is it more difficult to walk on sand than on a concrete pavement?

  1. (a) Sand has a higher coefficient of static friction than concrete.
  2. (b) Sand is less dense than concrete, causing less gravitational pull.
  3. (c) Sand displaces, reducing pushback.
  4. (d) Sand particles are magnetic, creating an opposing force.
Answer & solution

Answer: (c) Sand displaces, reducing pushback.

When you push against sand, its loose particles displace under your foot, so the ground gives way and provides less normal reaction (less push-back), making walking harder.
Density differences and magnetism are irrelevant; sand actually has a lower effective friction for walking due to displacement.
Hence, Option 3 is correct.
SSC CGL Tier-1 2025 – 14 September 2025 Shift 1 · Newton's first law and inertia

Q84. It is difficult to start motion with a heavy box and also difficult to stop it once it's moving. This best exemplifies:

  1. (a) Conservation of energy
  2. (b) Property of inertia
  3. (c) Action-reaction principle
  4. (d) Reaction principle
Answer & solution

Answer: (b) Property of inertia

The tendency of a body to resist a change in its state of rest or uniform motion is called inertia.
A heavy box has greater inertia (mass) — so it is hard to start moving (inertia of rest) and equally hard to stop once moving (inertia of motion).
Conservation of energy is unrelated to this resistance, and action–reaction (Newton's third law) is about paired forces, not resistance to a change in state.
Hence the property exemplified is inertia.
RRB NTPC UG CBT-1 2024-25 – 9 September 2025 Shift 2 · Friction

Q85. What is the direction of frictional force?

  1. (a) Along the normal to the contact surface
  2. (b) Opposite to the direction of relative motion
  3. (c) Perpendicular to the motion
  4. (d) Same as the direction of applied force
Answer & solution

Answer: (b) Opposite to the direction of relative motion

RRB NTPC UG CBT-1 2024-25 – 8 September 2025 Shift 2 · Newton's third law and its applications

Q86. Which of the following statements about action and reaction forces is correct?

  1. (a) Action and reaction forces act on the same body and cancel each other.
  2. (b) The internal action and reaction forces between different parts of a body do not cancel out.
  3. (c) Action is always greater than reaction in magnitude.
  4. (d) Action and reaction forces are equal, opposite and act on different bodies.
Answer & solution

Answer: (d) Action and reaction forces are equal, opposite and act on different bodies.

RRB NTPC UG CBT-1 2024-25 – 22 August 2025 Shift 1 · Impulse

Q87. Which of the following best defines impulse in mechanics?

  1. (a) The product of force and the time for which it acts
  2. (b) The product of mass and velocity
  3. (c) The rate of change of momentum multiplied by the distance
  4. (d) The change in displacement over time
Answer & solution

Answer: (a) The product of force and the time for which it acts

RRB NTPC UG CBT-1 2024-25 – 13 August 2025 Shift 2 · Friction

Q88. Which of the following statements about friction is correct?

  1. (a) Static friction opposes actual motion, while kinetic friction opposes impending motion.
  2. (b) Kinetic friction is always greater than static friction.
  3. (c) Static friction opposes impending motion and kinetic friction opposes actual motion.
  4. (d) Both static and kinetic friction depend on the area of contact.
Answer & solution

Answer: (c) Static friction opposes impending motion and kinetic friction opposes actual motion.

RRB NTPC UG CBT-1 2024-25 – 12 August 2025 Shift 1 · Impulse

Q89. Impulse is defined as _________.

  1. (a) rate of change of force
  2. (b) change in displacement
  3. (c) product of mass and velocity
  4. (d) product of force and time
Answer & solution

Answer: (d) product of force and time

SSC Selection Post 2025 (Phase XIII) – 30 July 2025 Shift 1 · Newton's third law and its applications

Q90. Which principle explains how rockets are propelled forward when fuel is ejected in the opposite direction?

  1. (a) Newton's First Law of Motion
  2. (b) Law of Conservation of Mass
  3. (c) Newton's Third Law of Motion
  4. (d) Law of Gravitation
Answer & solution

Answer: (c) Newton's Third Law of Motion

Correct Answer: Option 3 – Newton's Third Law of Motion
Newton's Third Law of Motion states: 'For every action, there is an equal and opposite reaction.' In rocket propulsion: the rocket engine burns fuel and expels hot exhaust gases backward at high velocity (action); the rocket is propelled forward by an equal and opposite force (reaction). This thrust force equals the rate of change of momentum of ejected gases (F = dp /dt). Rockets work even in vacuum because they carry their own propellant and oxidizer, relying only on Newton's Third Law — not air resistance or external support.
Option 1 (Newton's First Law): The Law of Inertia — objects continue in their state of rest/uniform motion unless acted upon by a net force. Explains why the rocket keeps moving once in space but not the propulsion mechanism.
Option 2 (Law of Conservation of Mass): Concerns that mass is neither created nor destroyed; not the principle explaining rocket propulsion direction.
Option 4 (Law of Gravitation): Newton's Universal Law of Gravitation explains gravitational attraction between masses — not rocket propulsion by ejected fuel.
SSC Selection Post 2025 (Phase XIII) – 26 July 2025 Shift 3 · Conservation of momentum and recoil

Q91. Which of the following scenarios best illustrates the principle of conservation of momentum?

  1. (a) A ball rolling down a frictionless incline increases its speed.
  2. (b) A car comes to a stop when the brakes are applied due to friction.
  3. (c) When a bullet is fired from a gun, the gun recoils in the opposite direction.
  4. (d) A satellite maintains a stable orbit around the Earth due to gravity.
Answer & solution

Answer: (c) When a bullet is fired from a gun, the gun recoils in the opposite direction.

Correct Answer: Option 3 – When a bullet is fired from a gun, the gun recoils in the opposite direction
Conservation of momentum: In the absence of external forces, total momentum of a system remains constant. Initial momentum of gun+bullet system = 0. After firing: bullet gains forward momentum (mv) and gun recoils backward with equal and opposite momentum (-MV), so total momentum remains zero. This is the classic application of Newton's Third Law and conservation of momentum.
Option 1 (Ball on incline): Illustrates conservation of energy (PE → KE) and Newton's Second Law; not momentum conservation.
Option 2 (Car braking): Friction is an external force acting on the car; the presence of external forces means this does NOT illustrate conservation of momentum.
Option 4 (Satellite orbit): Centripetal gravitational force keeps the satellite in orbit; illustrates circular motion dynamics, not conservation of momentum.
SSC Selection Post 2025 (Phase XIII) – 25 July 2025 Shift 3 · Conservation of momentum and recoil

Q92. Which of the following scenarios best illustrates the principle of conservation of momentum?

  1. (a) A ball rolling down a frictionless incline increases its speed.
  2. (b) A car comes to a stop when the brakes are applied due to friction.
  3. (c) When a bullet is fired from a gun, the gun recoils in the opposite direction.
  4. (d) A satellite maintains a stable orbit around the Earth due to gravity.
Answer & solution

Answer: (c) When a bullet is fired from a gun, the gun recoils in the opposite direction.

Correct Answer: Option 3 – When a bullet is fired from a gun, the gun recoils in the opposite direction
Conservation of momentum states that in the absence of external forces, the total momentum of a system remains constant. When a bullet is fired, the gun-bullet system has zero initial momentum. After firing: the bullet moves forward with momentum (mv) and the gun recoils backward with equal and opposite momentum (-MV), so total momentum remains zero. This is a classic demonstration of Newton's Third Law and conservation of momentum.
Option 1 (Ball on frictionless incline): This illustrates conservation of energy (potential → kinetic) and Newton's Second Law; not primarily momentum conservation.
Option 2 (Car braking): Friction is an external force acting on the car, decelerating it. External forces are present, so this does NOT illustrate conservation of momentum.
Option 4 (Satellite orbit): Maintained by gravitational force (centripetal); illustrates circular motion and gravitational forces, not conservation of momentum.
SSC Selection Post 2025 (Phase XIII) – 24 July 2025 Shift 2 · Newton's third law and its applications

Q93. Which statement best explains Newton's Third Law of Motion?

  1. (a) Force = mass × acceleration
  2. (b) Energy cannot be created or destroyed
  3. (c) For every action, there is an equal and opposite reaction
  4. (d) The acceleration is inversely proportional to mass
Answer & solution

Answer: (c) For every action, there is an equal and opposite reaction

Correct Answer: Option 3 – For every action, there is an equal and opposite reaction
Newton's Third Law of Motion states that for every action (force), there is an equal in magnitude and opposite in direction reaction force. The two forces act on different objects simultaneously. Examples: rocket propulsion (exhaust pushes down, rocket moves up), swimming (push water backward, move forward), walking (push ground backward, ground pushes forward).
Option 1 (Force = mass × acceleration): This is Newton's Second Law of Motion (F = ma).
Option 2 (Energy cannot be created or destroyed): This is the Law of Conservation of Energy (First Law of Thermodynamics); not Newton's Third Law.
Option 4 (Acceleration inversely proportional to mass): This is derived from Newton's Second Law (a = F/m); not Newton's Third Law.
RRB NTPC GL CBT-1 2024-25 – 5 June 2025 Shift 3 · Newton's first law and inertia

Q94. A body of mass 10 kg is moving with a uniform velocity of 5 m/s. What is the net force acting on it?

  1. (a) 0 N
  2. (b) 2 N
  3. (c) 50 N
  4. (d) 10 N
Answer & solution

Answer: (a) 0 N

RRB Technician Grade III 2024-25 – 30 December 2024 Shift 1 · Newton's second law and momentum

Q95. What is the momentum p, of an object of mass m, moving with a velocity v?

  1. (a) P = m v⁻²
  2. (b) P = v m⁻¹
  3. (c) P = m v
  4. (d) p = (mv)⁻²
Answer & solution

Answer: (c) P = m v

Correct Answer: Option 3 — P = m v
Momentum is the "quantity of motion" of a body. It is defined as the product of the mass of the body and its velocity:
p = m × v
It is a vector quantity whose direction is the same as that of the velocity, and its SI unit is kg m/s (equivalently N s). A loaded truck moving slowly and a light bullet moving very fast can both carry large momentum, because momentum depends on both mass and speed.
Momentum is the heart of Newton's second law, which says that the rate of change of momentum is proportional to the applied force: F = (mv − mu)/t = ma. It also gives the law of conservation of momentum — in the absence of an external force the total momentum of a system stays constant, which explains the recoil of a gun and the working of a rocket.
❌ Why the other options are incorrect
✗ P = m v⁻² — this is m/v², which would make momentum *decrease* as the body moves faster; the units kg s²/m² are meaningless here.
✗ P = v m⁻¹ — this is v/m, so a heavier body would have less momentum at the same speed, which contradicts everyday experience.
✗ p = (mv)⁻² — this is 1/(mv)², a completely different quantity with units of s²/(kg² m²); momentum is directly, not inversely, related to mass and velocity.
📌 SSC & Railway Exam Facts
• Momentum p = mv; SI unit kg m/s or N s; it is a vector.
• Newton's second law: F = dp/dt = ma; Impulse = F × t = change in momentum.
• Law of conservation of momentum: total momentum before = total momentum after, for an isolated system.
• Kinetic energy in terms of momentum: KE = p²/2m.
• Recoil velocity of a gun: m₁v₁ = m₂v₂, so a heavier gun recoils more slowly.
RRB Technician Grade III 2024-25 – 30 December 2024 Shift 1 · Numericals on force and momentum

Q96. If a force of 2 N gives a mass m₁, an acceleration of 8 m s⁻² and a mass m₂, an acceleration of 15 m s⁻² , what will be the total mass if both the masses were tied together?

  1. (a) 23/60 kg
  2. (b) 10/40 kg
  3. (c) 4/10 kg
  4. (d) 3/10 kg
Answer & solution

Answer: (a) 23/60 kg

Correct Answer: Option 1 — 23/60 kg
📖 Given
• Force applied in both cases, F = 2 N
• Acceleration of the first mass, a₁ = 8 m s⁻²
• Acceleration of the second mass, a₂ = 15 m s⁻²
✍️ Formula
Newton's second law: F = ma, so m = F/a
🔢 Solution
• m₁ = 2/8 = 1/4 kg
• m₂ = 2/15 kg
• Total mass = m₁ + m₂ = 1/4 + 2/15
• Taking LCM of 4 and 15 as 60: = 15/60 + 8/60
• Total mass = 23/60 kg
So the two bodies tied together weigh 23/60 kg ≈ 0.383 kg. (A check: the same 2 N force would now give them an acceleration of 2 ÷ 23/60 = 120/23 ≈ 5.2 m s⁻², less than either separate value — as expected for a bigger mass.)
❌ Why the other options are incorrect
✗ 10/40 kg — this is 1/4 kg, i.e. only m₁; the second mass has been left out.
✗ 4/10 kg — this is 0.4 kg, slightly more than the true answer; it comes from rounding 2/15 up to 0.15 and adding carelessly.
✗ 3/10 kg — 0.3 kg; obtained if you wrongly take m₂ = 2/15 as about 0.05 kg instead of 0.133 kg.
📌 SSC & Railway Exam Facts
• Newton's second law: F = ma = rate of change of momentum; SI unit of force is the newton (N).
• 1 N = 1 kg m s⁻² — the force that gives a 1 kg mass an acceleration of 1 m s⁻².
• For a fixed force, a ∝ 1/m: the heavier the body, the smaller its acceleration.
• When masses are tied together they move as one body of mass m₁ + m₂.
• Newton's first law defines inertia; the third law gives action = −reaction.
RRB Technician Grade III 2024-25 – 29 December 2024 Shift 1 · Numericals on force and momentum

Q97. If F₁ force is required to accelerate an object of 5 kg mass at 10 m s⁻² and F₂ force to accelerate an object of 10 kg mass at 12 m s⁻², then which of the following statements is true?

  1. (a) F₂ = −2 × F₁
  2. (b) F₁ = F₂
  3. (c) F₂ > F₁
  4. (d) F₁ > F₂
Answer & solution

Answer: (c) F₂ > F₁

Correct Answer: Option 3 — F₂ > F₁
📖 Given
• First object: mass m₁ = 5 kg, acceleration a₁ = 10 m s⁻², force F₁
• Second object: mass m₂ = 10 kg, acceleration a₂ = 12 m s⁻², force F₂
✍️ Formula
F = ma (Newton's Second Law of Motion)
🔢 Solution
• F₁ = m₁ × a₁ = 5 × 10
• F₁ = 50 N
• F₂ = m₂ × a₂ = 10 × 12
• F₂ = 120 N
• Comparing the two: 120 N > 50 N, so F₂ > F₁.
• In fact F₂/F₁ = 120/50 = 2.4, that is F₂ = 2.4 × F₁.
In plain words, the second object is both heavier and is being given a larger acceleration, so naturally it needs the bigger force.
❌ Why the other options are incorrect
✗ F₂ = −2 × F₁ — a negative force here has no meaning; also the actual ratio is +2.4, not −2. This option comes from only comparing the masses (10/5 = 2) and adding a stray minus sign.
✗ F₁ = F₂ — the two forces are 50 N and 120 N, clearly unequal.
✗ F₁ > F₂ — reversed; 50 N is smaller than 120 N.
📌 SSC & Railway Exam Facts
• Newton's Second Law: F = ma, also F = dp/dt (rate of change of momentum).
• SI unit of force is the newton (N); 1 N = 1 kg m s⁻² and 1 N = 10⁵ dyne.
• First Law (law of inertia) defines force; Third Law — every action has an equal and opposite reaction.
• Momentum p = mv; its SI unit is kg m s⁻¹, and it is a vector quantity.
• The newton is a derived SI unit; force is measured with a spring balance.
RRB Technician Grade III 2024-25 – 28 December 2024 Shift 1 · Newton's third law and its applications

Q98. 'When a sailor jumps out of a rowing boat, the boat moves backwards' is an example of which law of motion?

  1. (a) Law of inertia
  2. (b) Newton's second law of motion
  3. (c) Newton's first law of motion
  4. (d) Newton's third law of motion
Answer & solution

Answer: (d) Newton's third law of motion

Correct Answer: Option 4 — Newton's third law of motion
Newton's Third Law of Motion states that to every action there is an equal and opposite reaction, and the two forces act on two different bodies.
When the sailor jumps forward out of the boat, his feet push the boat backwards — that is the action. The boat in turn pushes the sailor forward with an equal force — that is the reaction. Since the boat is free to move on water, the backward push makes it move backwards while the sailor moves forward.
The same situation can also be read through the law of conservation of momentum: the total momentum of (sailor + boat) was zero before the jump, so after the jump the forward momentum of the sailor must be balanced by an equal backward momentum of the boat, m₁v₁ = m₂v₂.
Other everyday examples: the recoil of a gun, the motion of a rocket, and walking on the ground.
❌ Why the other options are incorrect
✗ Law of inertia — this is another name for the first law; it explains why a body resists a change in its state, not why the boat is pushed back.
✗ Newton's second law of motion — the second law, F = ma, tells how much acceleration a given force produces; it does not say that forces occur in pairs.
✗ Newton's first law of motion — the first law deals with a body at rest or in uniform motion when no unbalanced force acts; here a definite force does act.
📌 SSC & Railway Exam Facts
• Third law: action = −reaction; they are equal in magnitude, opposite in direction and act on different bodies, so they never cancel out.
• Second law: F = ma = rate of change of momentum (F = Δp/Δt).
• First law = Law of Inertia; mass is the measure of inertia.
• Rocket propulsion and the recoil of a gun are standard third-law PYQ examples.
• Law of conservation of momentum follows directly from the third law.
RRB Technician Grade III 2024-25 – 28 December 2024 Shift 2 · Newton's first law and inertia

Q99. The natural tendency of objects to resist a change in their state of rest or of uniform motion is called_______.

  1. (a) motion
  2. (b) momentum
  3. (c) inertia
  4. (d) force
Answer & solution

Answer: (c) inertia

Correct Answer: Option 3 — inertia
Inertia is the natural tendency of every body to resist any change in its state of rest or of uniform motion in a straight line. A body at rest wants to stay at rest and a body in motion wants to keep moving with the same speed in the same direction, until an unbalanced external force acts on it.
This idea is the content of Newton's First Law of Motion, which is therefore also called the Law of Inertia. The mass of a body is the direct measure of its inertia — a heavier body is harder to start and harder to stop.
Everyday examples: passengers jerk backwards when a bus starts suddenly (inertia of rest) and fall forward when it brakes suddenly (inertia of motion).
❌ Why the other options are incorrect
✗ motion — motion is simply the change of position of a body with time; it does not describe resistance to change.
✗ momentum — momentum is p = mv, the 'quantity of motion' a moving body carries; its SI unit is kg m/s.
✗ force — force is the external push or pull that overcomes inertia and changes the state of motion; its SI unit is the newton (N).
📌 SSC & Railway Exam Facts
• Newton's First Law = Law of Inertia; it was first stated in essence by Galileo.
• Mass is the measure of inertia — more mass means more inertia.
• Three types: inertia of rest, inertia of motion and inertia of direction.
• Newton's Second Law: F = ma; Third Law: action and reaction are equal and opposite.
• 1 newton is the force that gives a 1 kg mass an acceleration of 1 m/s².
RRB Technician Grade III 2024-25 – 28 December 2024 Shift 3 · Newton's second law and momentum

Q100. Which of the following options is the same as Newton's second law of motion?

  1. (a) The rate of change of momentum of an object is independent of the applied unbalanced force.
  2. (b) Applied force on a body is inversely proportional to the acceleration of the body.
  3. (c) An object at rest will remain at rest when external force is not applied.
  4. (d) If an object is in motion, applied force is directly proportional to the acceleration.
Answer & solution

Answer: (d) If an object is in motion, applied force is directly proportional to the acceleration.

Correct Answer: Option 4 — If an object is in motion, applied force is directly proportional to the acceleration.
Newton's Second Law of Motion states that the rate of change of momentum of a body is directly proportional to the applied unbalanced force, and the change takes place in the direction of the force.
Starting from momentum p = mv:
F ∝ Δp/Δt = m(v − u)/t = ma
So for a body of constant mass, F = ma. With the mass fixed, this means the applied force is directly proportional to the acceleration produced — exactly what option 4 says.
The same law fixes the size of the SI unit of force: 1 newton is the force that produces an acceleration of 1 m/s² in a mass of 1 kg, so 1 N = 1 kg m/s².
❌ Why the other options are incorrect
✗ The rate of change of momentum of an object is independent of the applied unbalanced force. — this is the exact opposite of the second law; the rate of change of momentum is directly proportional to that force.
✗ Applied force on a body is inversely proportional to the acceleration of the body. — the relation F = ma is a direct proportionality, not an inverse one; more force gives more acceleration.
✗ An object at rest will remain at rest when external force is not applied. — this is the statement of Newton's First Law (law of inertia), not the second law.
📌 SSC & Railway Exam Facts
• Second law: F = ma = Δp/Δt; force and acceleration are in the same direction.
• 1 newton = 1 kg m/s²; the CGS unit is the dyne, and 1 N = 10⁵ dyne.
• Momentum p = mv, a vector, SI unit kg m/s.
• Impulse = F × t = change in momentum; this is why cricketers draw their hands back while catching a ball.
• The second law gives a quantitative measure of force; the first law only defines force qualitatively.
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