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Potential Energy is Negative?

  1. May 30, 2014 #1
    we have an inversed pendulum(ignore the car)
    and we choose the coordinate system to be upwards
    the potential energy PE=mgz (z will be hegative since( O,k) is upwards right?) z is always under O.
    but in the text book they basically take the absolute value of h i don't understand why?
    Last edited: May 30, 2014
  2. jcsd
  3. May 30, 2014 #2
    Where is the text book putting the zero of h?
  4. May 30, 2014 #3
    at the point of rest of the pendulum (same as O)
  5. May 30, 2014 #4
    fixed the problem (h ad to do with angle being negatgive which means the work of p is negative)
    sorry my explication of the question was off , close this thread
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