Question

A person getting out of the moving bus or a train falls in the forward direction. This is an example of
(A) Second law of motion
(B) Third law of motion
(C) Inertia of rest
(D) Inertia of motion

Answer 1

Hint: Recall Newton’s first law of motion. Due to inertia, the body in the motion stays in the motion unless it is affected by the external opposing force.And applying it according to the given options.

Complete step by step answer:
According to Newton’s first law of motion, the body in the motion stays in the motion unless and until it is acted by the external force to oppose its motion.
Inertia of the body is the tendency of the body to continue its motion even after the applied force on the body is removed.While the person is in the bus or the train, he moves in the same direction of motion as the motion of the train. When the person steps on the ground, his feet do not move but his upper body moves in the direction of the train due to inertia of its motion. Since his upper body moves in the forward direction and his lower body does not move, the person falls in the forward direction.We need to verify other options as well.
Second law of motion:
Newton’s second law of motion states that the rate of change of momentum of the body with respect to time is equal to the force applied on that body.
The person getting out of the moving bus does not fall in the forward direction due to applied force.Therefore, the option (A) is incorrect.
Third law of motion:
According to the third law of motion, the force exerted on the body also exerts the equal force on the first body in the opposite direction.
This does not explain why the person getting out of the moving train falls in the forward direction.Therefore, the option (B) is incorrect.
Inertia of rest:
Inertia of rest implies that the body in the rest remains in the rest unless and until it is acted upon by the external force.But here the person is getting out of the moving train is in motion.Therefore, the option (C) is incorrect.
So, the correct option is (D).

Note:The phenomenon of inertia of rest and inertia of motion are completely different. The inertia of rest is due to the rest position of the body and the inertia of motion is due to the motion of the body.