Question

In a shopping mall, two elevators pass each other moving in opposite directions. Each elevator is moving at the same speed. The relative velocity of one elevator to another is 10 m/s. what is the velocity of each elevator to a person standing on the ground?

Answer 1

Answer:

5 m/s upward and 5 m/s downward

Explanation:

Let's call v the speed of each elevator. So one elevator is moving with velocity +v relative to the ground (the positive sign indicates the upward direction) and the other one with velocity -v relative to the ground (downward direction).

The relative velocity of one elevator to another is 10 m/s, so we can write:

$+v = -v + 10$

which means

$+2v=10\\v = 5 m/s$

So the speed of each elevator relative to the ground is 5 m/s, with one moving upward and the other one moving downward.