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## Homework Statement

A 900 kg roller-coaster car is initially at the top of a rise, at point A. It then moves 165 ft, at an angle of 40.0° below the horizontal, to a lower point B.

Choose the car at point B to be the zero configuration for gravitational potential energy of the roller coaster-Earth system. Find the potential energy of the system when the car is at points A and B, and the change in potential energy as the coaster moves.

## Homework Equations

U=mgy

## The Attempt at a Solution

I've found that the potential energy at point B is 0 (obviously), but I can't find it at A.

I'm pretty sure it's U=900(9.8)h

But I'm not sure how to find the height. Wouldn't it be something like 165sin40?

**Edit:**D'oh. Figured it out. the distance is in feet, gotta convert it to meters. Stupid conversions. :P

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