Question

Two people are on a train that is moving at 10 m/s north. They are walking 1 m/s south relative to the train. Relative to the ground, their motion is 9 m/s north. Why are we able to use these motions to describe the motion relative to the ground? (1 point) Responses As long as the frame of reference is stationary, all motion can be described in this way. As long as the frame of reference is stationary, all motion can be described in this way. The people are moving much slower than the speed of light so the ground acts as a frame of reference. The people are moving much slower than the speed of light so the ground acts as a frame of reference. If one object is moving much slower than the speed of light, its speed can be added to that of another object. If one object is moving much slower than the speed of light, its speed can be added to that of another object. The motion of everything in the Universe besides light can be described in this way.

Answer 1

The correct response is: If one object is moving much slower than the speed of light, its speed can be added to that of another object.

This response accurately captures the classical mechanics concept of adding velocities, which holds true when the speeds involved are much smaller than the speed of light. In this situation, the train's speed and the persons' speed can be combined using simple arithmetic to find their speed relative to the ground.