Gravitational ep in a uniform field

[kelly242]

Homework Statement

A 10.0 kg box is slid down15.0 m along a 20.0o ramp. The force of friction is 40.0 N. What is the change in the gravitational potential energy of the box?

Homework Equations

W=Fdcos of theta

The Attempt at a Solution

W=(40 N)(15 m)(cos 20)
=563.8J
The actual answer is -503 J...

 

[TobeHode]

Try:

V = mgh

Then just figure out what the initial height is.