Newtons third law of motion, law of conservation of linear momentum and applications - Question Bank

1. During a collision between two bodies in an isolated system, the total momentum of the system immediately after the collision is:
A) Greater than the total momentum before the collision.
B) Less than the total momentum before the collision.
C) Equal to the total momentum before the collision.
D) Dependent on the nature of the collision (elastic or inelastic).
2. A rocket expels gases at a high velocity. This expulsion is the action force. The reaction force is the thrust that propels the rocket forward. This is a clear application of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law.
D) Conservation of energy.
3. If a system is subjected to an external force, its total linear momentum will:
A) Remain constant.
B) Change.
C) Become zero.
D) Increase indefinitely.
4. The law of conservation of linear momentum is applicable to:
A) Only isolated systems.
B) Only systems with no external forces.
C) Any system, provided we consider all internal and external forces.
D) Systems where the net external force is zero.
5. When a person stands on a boat and throws a stone forward, the boat moves backward. This is an example of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law and conservation of linear momentum.
D) Conservation of angular momentum.
6. A cannonball is fired from a cannon. If the mass of the cannon is M and the mass of the cannonball is m, and their velocities immediately after firing are V and v respectively, then by conservation of momentum:
A) MV = mv
B) MV = -mv
C) Mv = mV
D) M + m = V + v
7. In a collision between two objects, the forces they exert on each other are equal and opposite. This means the impulses they exert on each other are also:
A) Equal and in the same direction.
B) Equal and in opposite directions.
C) Unequal and in opposite directions.
D) Zero.
8. The impulse delivered to an object is equal to the change in its:
A) Kinetic energy.
B) Potential energy.
C) Linear momentum.
D) Angular momentum.
9. If a system consists of only internal forces, its total linear momentum:
A) Changes with time.
B) Remains constant.
C) Becomes zero.
D) Is proportional to the square of time.
10. A child jumps from a moving train onto the platform. To land safely, the child should jump:
A) Forward with the train's velocity.
B) Backward against the train's motion.
C) Vertically downwards.
D) As fast as possible.
11. Consider two masses, m1 and m2, connected by a string passing over a frictionless pulley (Atwood machine). If m1 > m2, both masses accelerate. The force exerted by the string on m1 is:
A) Equal to the force exerted by the string on m2.
B) Less than the tension in the string.
C) Equal to the tension in the string.
D) Equal and opposite to the force exerted by m1 on the string.
12. When a boat moves forward, the person on the boat pushes the water backward. This is an example of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law.
D) Archimedes' principle.
13. A system is isolated if the vector sum of all external forces acting on it is zero. In such a system, the total linear momentum is:
A) Zero.
B) Constant.
C) Proportional to time.
D) Inversely proportional to time.
14. An astronaut in space pushes a heavy object away from themselves. Both the astronaut and the object move in opposite directions. This is a demonstration of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law and conservation of linear momentum.
D) Conservation of angular momentum.
15. Two particles A and B collide. If the momentum of A changes by Δp, then the momentum of B changes by:
A) Δp
B) -Δp
C) 2Δp
D) Zero
16. The rate of change of linear momentum of a system is equal to:
A) The net internal force.
B) The net external force.
C) The sum of impulses.
D) The total kinetic energy.
17. A fire hose sprays water. The hose tends to move backward as the water is expelled forward. This is because:
A) The water is heavier than the hose.
B) The force exerted by the hose on the water is met by an equal and opposite force exerted by the water on the hose.
C) The pressure of the water is high.
D) Friction between the water and the nozzle.
18. When you jump off a cliff, you accelerate downwards due to gravity. The Earth also accelerates towards you, but its acceleration is negligible due to its immense mass. This illustrates:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law.
D) The principle of inertia.
19. Consider a system of two particles interacting only with each other. If the initial momentum of the system is P, then the final momentum of the system after interaction will be:
A) Greater than P
B) Less than P
C) Equal to P
D) Zero
20. In a perfectly elastic collision between two identical objects, the total momentum is conserved. What about kinetic energy?
A) Kinetic energy is not conserved.
B) Kinetic energy is conserved.
C) Kinetic energy is converted into heat.
D) Kinetic energy is converted into potential energy.
21. A person is standing on a skateboard. When the person throws a ball horizontally, the skateboard moves backward. This is an application of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law and conservation of linear momentum.
D) Conservation of angular momentum.
22. If the net external force on a system is zero, then the velocity of the center of mass of the system:
A) Is always zero.
B) Is always changing.
C) Remains constant.
D) Is equal to the average velocity of the particles.
23. The law of conservation of linear momentum is a direct consequence of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law.
D) Both Newton's second and third laws.
24. A gun recoils when a bullet is fired. If the gun were much heavier, its recoil velocity would be:
A) Higher than before.
B) Lower than before.
C) The same as before.
D) Zero.
25. Consider a collision between two particles. The impulse experienced by particle 1 is equal and opposite to the impulse experienced by particle 2. This is a direct consequence of:
A) Conservation of energy.
B) Newton's third law.
C) Newton's second law.
D) Conservation of mass.
26. If a net force acts on a system, the total momentum of the system:
A) Remains conserved.
B) Changes at a rate equal to the net force.
C) Changes at a rate equal to the net force divided by time.
D) Changes at a rate equal to the net force multiplied by time.
27. A rocket works on the principle of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law and conservation of linear momentum.
D) Conservation of angular momentum.
28. A system of particles is said to be isolated if:
A) The total energy of the system is conserved.
B) The net work done on the system is zero.
C) The sum of all external forces acting on the system is zero.
D) The particles within the system do not interact with each other.
29. Two skaters, A and B, are initially at rest on a frictionless surface. Skater A pushes skater B. According to Newton's third law, if the mass of A is greater than the mass of B, then:
A) The acceleration of A is greater than the acceleration of B.
B) The acceleration of B is greater than the acceleration of A.
C) The magnitude of acceleration of A is less than the magnitude of acceleration of B.
D) The force exerted by A on B is greater than the force exerted by B on A.
30. When a person stands on a boat, the total momentum of the person-boat system is zero if they are initially at rest. If the person starts walking towards the bow, the boat will move towards the stern to conserve momentum. This demonstrates:
A) Newton's second law.
B) The law of conservation of linear momentum.
C) The law of conservation of angular momentum.
D) The effect of buoyancy.
31. A bird flies by pushing air downwards. This action results in an upward reaction force from the air on the bird, enabling flight. This is an example of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law.
D) Bernoulli's principle.
32. If two objects of masses m1 and m2 are moving with velocities v1 and v2 respectively, and they collide and stick together (inelastic collision), the total momentum before collision is conserved and is equal to the momentum after collision, provided the system is isolated. The momentum after collision is:
A) (m1+m2)v1
B) (m1+m2)v2
C) (m1+m2)(v1+v2)
D) (m1+m2)V, where V is the final velocity of the combined mass.
33. A spacecraft releases a probe. Both the spacecraft and the probe move away from each other. This is because:
A) The probe is lighter than the spacecraft.
B) The spacecraft exerts a force on the probe, and the probe exerts an equal and opposite force on the spacecraft.
C) The probe's engine is activated.
D) The release mechanism imparts momentum to both.
34. When walking, a person pushes backward on the ground. The ground, in turn, pushes forward on the person. This forward push is the force that allows the person to move. This is an application of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law.
D) The law of conservation of energy.
35. Consider a rifle firing a bullet. The recoil of the rifle is due to:
A) The bullet exerting a force on the rifle.
B) Newton's third law, where the rifle exerts a force on the bullet, and the bullet exerts an equal and opposite force on the rifle.
C) The conservation of kinetic energy.
D) Air resistance acting on the bullet.
36. A system consists of two particles. If there are no external forces acting on the system, the center of mass of the system:
A) Must be at rest.
B) Must move with constant velocity.
C) Must accelerate.
D) May be at rest or move with constant velocity.
37. If the net external force on a system is zero, then:
A) The kinetic energy of the system is zero.
B) The total momentum of the system is conserved.
C) The velocity of the system is zero.
D) The acceleration of the system is zero.
38. During a collision between two objects, the net impulse on object 1 is equal and opposite to the net impulse on object 2. This is a consequence of:
A) Conservation of energy.
B) Newton's third law.
C) Conservation of mass.
D) Newton's first law.
39. A boat is floating on water. When a person jumps from the boat to the shore, the boat moves backward. This is an example of:
A) Newton's first law.
B) Newton's second law.
C) Newton's third law and conservation of linear momentum.
D) Conservation of angular momentum.
40. A bomb explodes into several fragments. If we ignore air resistance, the total momentum of all fragments immediately after the explosion is:
A) Greater than the momentum of the bomb before explosion.
B) Less than the momentum of the bomb before explosion.
C) Equal to the momentum of the bomb before explosion.
D) Zero if the bomb was initially at rest.
41. Which of the following quantities is conserved in an isolated system according to the law of conservation of linear momentum?
A) Kinetic energy
B) Potential energy
C) Linear momentum
D) Angular momentum
42. A particle of mass 'm' moving with velocity 'v' has a linear momentum 'p'. If its velocity doubles, its new momentum will be:
A) p/2
B) p
C) 2p
D) 4p
43. Consider a collision between two billiard balls. If we consider the two balls as an isolated system, the total linear momentum *before* the collision is:
A) Different from the total linear momentum *after* the collision.
B) Equal to the total linear momentum *after* the collision.
C) Zero if the balls come to rest after collision.
D) Dependent on the coefficient of restitution.
44. An isolated system is defined as a system where:
A) No work is done on the system.
B) No energy is transferred into or out of the system.
C) No external forces act on the system.
D) The total mass of the system is constant.
45. The law of conservation of linear momentum states that:
A) The momentum of an object can never change.
B) The total momentum of an isolated system remains constant.
C) Momentum is always equal to mass times velocity.
D) The net force acting on an object is equal to its momentum.
46. When you push a wall, the wall pushes back on you with an equal and opposite force. This prevents you from moving through the wall because:
A) The wall is much more massive than you.
B) The force you exert is an action, and the wall's push is the reaction.
C) The reaction force from the wall is equal and opposite to your push.
D) Friction between your shoes and the ground prevents motion.
47. Which of the following statements is TRUE regarding the forces in Newton's third law?
A) The action and reaction forces act on the same object.
B) The action and reaction forces are always balanced.
C) The action and reaction forces act on different objects.
D) The action force is always greater than the reaction force.
48. A cannon fires a cannonball. Immediately after firing, the cannon recoils backward. This recoil is a direct consequence of:
A) Newton's first law of motion.
B) Newton's second law of motion.
C) Newton's third law of motion.
D) The law of conservation of energy.
49. Consider two objects, A and B, interacting with each other. According to Newton's third law, the force exerted by A on B is:
A) Always greater than the force exerted by B on A.
B) Always less than the force exerted by B on A.
C) Always equal in magnitude and opposite in direction to the force exerted by B on A.
D) Zero if the objects are not moving.
50. Newton's third law of motion states that for every action, there is an equal and opposite reaction. Which of the following scenarios best illustrates this law?
A) A car accelerating forward due to its engine.
B) A rocket expelling gas downwards to propel itself upwards.
C) A ball rolling down a frictionless inclined plane.
D) A book resting on a table.
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