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Homework Help: Dumbell problem (conservation of energy)

  1. Oct 7, 2016 #1
    1. The problem statement, all variables and given/known data


    A dumbell is leaned vertically on the wall. After it is deviated with some angle θ, dumbell starts sliding.
    Determine the angle between the bar and the horizontal face (floor) when the upper mass starts to fall.

    2. Relevant equations

    E = E'

    3. The attempt at a solution


    I don't understand how come there is mgL cos θ??
    I think the potential should be mg L sin θ, right??

    Please help
  2. jcsd
  3. Oct 7, 2016 #2


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    Science Advisor
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    Gold Member

    Right. Do you know how to finish the problem?
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