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.
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