A 1200-kg roller coaster car is initially at the top of a rise, at point circle a. It then moves 145 ft, at an angle of 40.0° below the horizontal, to a lower point circle b.

Question

(a) Choose the car at point circle 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 circle a and circle b, and the change in potential energy as the coaster moves between these points.
at point circle a J
at point circle b J
change in potential energy J

(b) Repeat part (a), setting the zero configuration with the car at point circle a
at point circle a J
at point circle b J
change in potential energy J

Answer 1

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Answer 2

I used the gravitational potential formula and plugged in 1200 * 9.8 * 45.31