Question

A man getting down from a running bus falls forward:
(A) As the forward movement of bus tries to pull the man forward
(B) Due to inertia the upper part of the body moves in the forward direction while feet come to rest as soon as they touch the road.
(C) As he leans forward as a matter of habit.
(D) Due to the combination effect of all the three factors stated in (A), (B) and (C).

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.

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, he moves in the same direction of motion as the motion of the bus. When the person steps on the ground, his feet do not move but his upper body moves in the direction of the bus 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.
(A) The forward movement of the bus does not act after the man steps out of the moving bus. It is the inertia of motion which brings him forward after getting out from the moving bus.Therefore, the option (A) is incorrect.
(B)While the person is in the bus, he moves in the same direction of motion as the motion of the bus. When the person steps on the ground, his feet do not move but his upper body moves in the direction of the bus 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.
(C) A person never leans forward as a matter of habit.Therefore, the option (C) is incorrect.

So, the correct answer is option (B).

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.