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## Homework Statement

After scoring a touchdown, an

84.0-kg wide receiver celebrates by leaping

1.20 m off the ground. How much work

was done by the wide receiver in the

celebration?

## Homework Equations

W= FD

## The Attempt at a Solution

I know that the correct answer should be:

(84.0 kg)(9.80 m/s2)(1.20 m)=988 J

I'm just wondering why the acceleration for the wide-receiver is 9.8m/s^2.

If his acceleration is 9.8 and the acceleration of gravity is 9.8, wouldn't the total acceleration be 0? Also, when a person jumps, he starts off with a positive velocity which decreases, so shouldn't his acceleration be negative?