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Homework Help: Change in potential energy on a roller coaster drop (frictionless)

  1. Oct 20, 2008 #1
    800 kg roller coaster is initially at the top of a rise, at point A. It then moves 125 ft (38.1 m), at an angle of 40.0° below the horizontal, to a lower point, B.

    (a) Choose point B to be the zero level for gravitational potential energy. Find the potential energy of the roller coaster-Earth system at points A and B and the change in potential energy as the coaster moves.

    To start, I aimed to find the potential energy at point A:
    Ug = mgh
    Ug = (800)(9.8)(y component of h)
    Ug = (800)(9.8)(38.1sin40)
    Ug = 222561.92 J

    What am I missing in my process? Thanks in advance.
  2. jcsd
  3. Oct 20, 2008 #2

    Doc Al

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    Staff: Mentor

    Everything looks good except your final answer. Redo that calculation.
  4. Oct 20, 2008 #3


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    Homework Helper

    I think your vertical drop calculation is in error. Your answer suggests the original height was 44.1m when the problem says it was 38.1m
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