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Homework Help: Difficult Centripetal Motion Problem

  1. Nov 13, 2012 #1
    1. The problem statement, all variables and given/known data
    Tarzan swings from a vine 20 m long which makes an angle of 30° with the vertical. If he pushes off with a speed of 2 m/s, what is the tension in the vine at the lowest point of the swing? Tarzan has a mass of 80 kg.

    2. Relevant equations
    centripetal accelaration force = F
    m = mass
    r = radius of circle
    v = tangential speed

    1/2mv^2 + mgh = 1/2mv^2 (I'm not sure about this, though)

    3. The attempt at a solution
    F = 80 (2^2)/ 20
    F = 16 N

    I don't know how to integrate the angle measure into the problem.
  2. jcsd
  3. Nov 13, 2012 #2


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    Homework Helper

    The 1/2mv^2 + mgh = 1/2mv^2 looks good. Use it to find the velocity at the lowest point. Then use Fc=m(v^2)/r with that value for v. Another force will add to this to make the total tension.
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