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)
We are able to use these motions to describe the motion relative to the ground because they are given with respect to a common reference point, which is the train. By combining the individual motions of the train and the people, we can determine their resulting motion relative to the ground.
