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## Homework Statement

I work as a supplemental instructor for an intro physics class. As I was preparing my worksheet for this week I came across this problem.

A basketball player can jump to a height of 55cm. How far above the floor can he jump in an elevator that is descending at a constant 1.0m/s.

## Homework Equations

v

_{f}

^{2}= v

_{i}

^{2}+ 2aΔx

## The Attempt at a Solution

First I used the above equation to determine the initial velocity the basketball player would need to achieve a height of 55cm on steady ground: 3.28m/s.

I then said that relative to the floor of the elevator the player is moving at 4.28m/s initially.

Thus his max height should be 93cm.

However, the answer in the back of the textbook says that the answer is 55cm (same as his normal jump height).

So that makes sense if the elevator is already moving when he jumps. Then his velocity before the jump is already -1m/s, offsetting the fact that the elevator is moving away from him after he jumps.

If the elevator begins moving the instant after he begins jumping, would my original solution be correct?

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