An elevator moving down passes its neighbor, an elevator moving up. Their speed relative to one another is 8 m/s. What is the velocity of each elevator relative to someone standing on the first floor? Assume that the elevators are traveling at the same speed, and that the upward direction is positive.
OPTIONS
One elevator is moving at 8 m/s; the other elevator is moving at -8 m/s.
Both elevators are moving at 4 m/s.
Both elevators are moving at 8 m/s.
One elevator is moving at 4 m/s; the other elevator is moving at -4 m/s.

Question

An elevator moving down passes its neighbor, an elevator moving up. Their speed relative to one another is 8 m/s. What is the velocity of each elevator relative to someone standing on the first floor? Assume that the elevators are traveling at the same speed, and that the upward direction is positive.
OPTIONS
One elevator is moving at 8 m/s; the other elevator is moving at -8 m/s.
	Both elevators are moving at 4 m/s.
	Both elevators are moving at 8 m/s.
	One elevator is moving at 4 m/s; the other elevator is moving at -4 m/s.

agent0smith · Answer

What do you think?

Think about two cars heading toward each other, each at 60mph. The driver of each car sees the other approaching at 120mph.