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Gravitational potential energy of tarzan

  1. Feb 19, 2007 #1
    1. The problem statement, all variables and given/known data

    Tarzan, in one tree, sights Jane in another tree. He grabs the end of a vine with length 20 m that makes an angle of 45 degrees with the vertical, steps off his tree limb, and swings down and then up to Jane's open arms. When he arrives, his vine makes an angle of 30 degrees with the vertical.

    Calculate Tarzan's speed just before he reaches Jane. You can ignore air resistance and the mass of the vine.

    2. Relevant equations
    K_1 + U_1= K_2 + U_2

    h= ((v_0)^2(sin^2))/(2g)

    3. The attempt at a solution

    i don't know how to relate the angles with this problem?
  2. jcsd
  3. Feb 19, 2007 #2


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    Staff Emeritus
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    Gold Member

    Then don't worry about it. Just try to solve the problem.

    Incidentally, where did

    h= ((v_0)^2(sin^2))/(2g)

    come from? (sin^2) doesn't even make sense!

    (Okay, technically it does make sense, but you almost certainly did not mean what that expression means)
  4. Feb 19, 2007 #3
    Draw a vertical line on piece a paper. Then draw an intersecting line downward and to the left at an angle of 45 degrees to the original line. Then draw another line outward from the same intersection point downward and to the right at 30 degrees to the original line. Now the pivot point for the vine is where the lines intersect and Tarzan swings on the vine in a circular path on a 20m long vine from the 45 degree line to the 30 degree line. So figure out the change in height, and calculate the kinetic energy from the change in potential energy.
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