Question

Your body has _______, and so a force is needed to change its velocity. The train floor accelerates your feet but your body fall backward​.

A) momentum
B) inertia
C) mass
D) weight

Answer 1

B) Inertia
Since all objects with mass have inertia, a force needs to be applied to cause a change in velocity. Since the force is applied to the feet, the feet change in velocity, but the force is not applied to the body and so it does not change in velocity with the feet, causing you to fall backwards.

Answer 2

The correct answer is B) inertia. Inertia is the property of a body to resist changes to its state of motion, and it is the reason why a person feels like falling backward when a train accelerates quickly.

Step-by-step explanation:

Inertia is a property of matter that describes the tendency of a body to resist changes to its state of motion. The momentum of a body, which is the product of its mass and velocity, can only change under the action of an outside influence, according to Newton's second law of motion. This law expresses force in terms of its ability to change momentum over time. When you are standing on a train that suddenly starts moving, the floor accelerates and your feet with it, but the inertia of the rest of your body resists this change in motion, causing you to feel like you're falling backward until the rest of your body catches up with your feet.