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) 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. the people are moving much slower than the speed of light so the ground acts as a frame of reference. as long as the frame of reference is stationary, all motion can be described in this way.

Explanation:

According to the principle of Galilean relativity, when objects are moving at speeds much slower than the speed of light (\(c = 3\times10^{8}\ m/s\)), velocities can be simply added or subtracted. In this case, the train's speed (\(v_{train}=10\ m/s\) north) and the people's speed relative to the train (\(v_{people - train}=1\ m/s\) south) are much slower than the speed of light. So, we can use the formula \(v_{people - ground}=v_{train}+v_{people - train}\) (taking north as positive, \(v_{people - ground}=10+( - 1)=9\ m/s\) north). The ground acts as a frame of reference, and since the speeds involved are non - relativistic (much less than \(c\)), we can add the velocities.

Answer:

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