Question

A man is sitting in a moving train, then:
$
{\text{A}}{\text{. his momentum must not be zero}} \\
{\text{B}}{\text{. his kinetic energy is zero}} \\
{\text{C}}{\text{. his kinetic energy is not zero}}{\text{.}} \\
{\text{D}}{\text{. his kinetic energy may be 0}}{\text{.}} \\
$

Answer 1

Hint:While sitting in a moving train, relative motion will come into picture and therefore, the answers will be given by viewing from the ground frame.

Complete answer:
Momentum is the product of mass and velocity. Any object having mass and pursuing motion is having momentum.

Kinetic energy is possessed by any object in motion.
It is given that the person is sitting in a train and that train is in motion. This implies that the train is also carrying the person concerned. This way the person is also moving.
But perseverance gets different when, frame is changed. For a viewer sitting in the train-
The train is not moving and neither the passengers sitting in the same train are moving. But the whole rest of the world is in motion.
While for any viewer standing outside the train, the train is in motion and so are the passengers sitting in it. This way, the person concerned has a momentum for a ground frame viewer.
If there is motion, then there is kinetic energy.
So, any person in a train when viewed from outside the train has momentum and kinetic energy.

So, the correct answer is “Option A and C”.

Note:
It is a default parameter to look from the ground state unless stated.
Everything in the universe possesses momentum and kinetic energy. It is just that only when you look from the object’s frame of reference it seems still otherwise, every particle is in a dynamic state.