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Tarzan problem

  1. Jan 9, 2007 #1
    "Tarzan" problem

    1. The problem statement, all variables and given/known data
    "Tarzan (m=85kg) tries to cross a river by swinging from a 10.0m long vine. His speed at the bottom of the swing, just as he clears the water, is 8.0 m/s. Tarzan doesn't know that the vine has a breaking strength of 1.0 x 10^3 N Does he make it safely across the river? Justify your answer."


    2. Relevant equations
    [tex]F_{c}=\frac{mv_{t}^2}{r}[/tex]


    3. The attempt at a solution
    I attempted to substitute in the variables as such:
    [tex]F_{c}=\frac{85kg*\left(8.0\frac{m}{s}\right)^2}{10.0m}[/tex]
    I got 544N, which is not the answer(1.37x10^3N is his 'weight' at this point, greater than the rope). Am I missing something obvious?
     
  2. jcsd
  3. Jan 9, 2007 #2

    Gib Z

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    You do not have the right formula. You are thinking of Centripetal Force, this is Pendulum Motion.
     
  4. Jan 9, 2007 #3

    PhanthomJay

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    You have correctly identified the centripetal force as 544N. The centripetal force is the net force acting up toward the center of the circle. The net force is a combination of the tension force up and his weight (not his 'weight' as you have described...his weight is m*g) down. Solve for T. Does the rope break?
     
  5. Jan 9, 2007 #4

    ShawnD

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    This is correct. Add 544N to (85 x 9.8) and you get 1377N
     
  6. Jan 9, 2007 #5

    Gib Z

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    Is it too late to pretend I havent said anything? eep my bad, just ignore anything i say
     
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