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Swinging from a vine (circular motion/tension problem)

  1. Oct 2, 2008 #1
    Tarzan (m = 85.0 kg) tries to cross a river by swinging from a vine. The vine is 10.5 m long, and his speed at the bottom of the swing (as he just clears the water) is 9.00 m/s. Tarzan doesn't know that the vine has a breaking strength of 1000 N. Find the tension on the vine. Does he make it safely across the river?

    m = 85.0 kg, r = 10.5 m, v = 9.00 m/s, T = ?
    fc = mac, ac = v2/r, therefore fc = mv2/r

    sigma f = m(v2/r)
    T - mg = m(v2/r)
    T - (85)(9.8) = (85)(92)/(10.5)
    T - (833) = 655.714
    T = 1488.71, no

    Solution is wrong. Can someone point me in the right direction, or point out my mistakes? Thanks in advance!
     
    Last edited: Oct 2, 2008
  2. jcsd
  3. Oct 2, 2008 #2

    LowlyPion

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    Welcome to PF.

    The only fault I can see from what is given is that there are 2 places after the decimal, when the least precision given was only 1 past the decimal.

    Unless they want the answer No and a tension of 0 because the vine broke and he's swimming with the crocs.
     
  4. Oct 2, 2008 #3

    tiny-tim

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    Welcome to PF!

    Hi Welcome to PF! Welcome to PF! :smile:

    hmm :rolleyes: … looks right to me …

    have you tried just 1489 ? :smile:
     
  5. Oct 2, 2008 #4

    LowlyPion

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    Re: Welcome to PF!

    Well ... all values have at least 1 after the decimal.
     
  6. Oct 2, 2008 #5

    tiny-tim

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    Hi LowlyPion! :smile:

    yes, but they're all 3-sig-figs …

    so I thought it was worth a try! :wink:
     
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