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Tarzan Physics Question with Kinematics, Energy, Forces

  1. Jun 16, 2012 #1
    1. The problem statement, all variables and given/known data
    Tarzan (63.0 kg) is trying to save Jane (50.0 kg) from the fast approaching crocodile (who is in the crocodile pit). Tarzan starts from rest at point A and swings off the edge of a cliff 30.0 m above the ground, while hanging on to a vine of a very large tree. At point B, Tarzan grabs Jane who is standing on the ground at the base of the tree (unaware of the approaching croc). Tarzan does not hit the tree. However, clumsy Tarzan loses grip of Jane at point C (the point where the ground and the crocodile pit meets), which is 12 m off the ground. Jane propels into the air at an angle 65 m above the horizontal and she follows a parabolic trajectory. The far side of the crocodile pit is horizontal distance of 5.5 m from point C. Assume no air resistance and the swinging vine is 100% efficient.

    Tarzany.jpg

    1. What is the velocity of Jane at point C, when Tarzan let her go?

    2. What is the maximum height that she reaches above the crocodile pit?

    3. Does Jane make it past the crocodile pit safely?

    4. What is Jane's final velocity upon landing.


    So I have a exam, which will have a Question similar to this one. I just don't know to get started with it.
     
  2. jcsd
  3. Jun 16, 2012 #2
    for the swinging thru air part, you can use conservation of mechanical energy (tension is perpendicular to motion, so there are no forces (gravity is represented by potential energy)).

    Notice you do not have conservation of momentum.

    However, during the short and sweet collision, you do not have conservation of mechanical energy (only in elastic collisions), but, since all external forces are negligible compared to the huge forces of collision, you have conservation of momentum.

    So for the first part of swinging, cons of energy, during the collision, cons of mom, second part of swining, cons of energy again.
     
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