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Force for uniform circular motion

  1. Feb 12, 2008 #1
    [SOLVED] Force for uniform circular motion

    1. The problem statement, all variables and given/known data
    A 61.7 kg ice skater is moving at 3.55 m/s when she grabs the loose end of a rope, the opposite end of which is tied to a pole. She then moves in a circle of radius 0.545 m around the pole. The acceleration of gravity is 9.8 m/s^2.
    a. Find the force exerted by the rope on her arms. Answer in units of kN.
    b. Find the ratio of this tension to her weight.

    2. Relevant equations
    F=(mv^2)/r


    3. The attempt at a solution
    I got a using the above equation:
    F=((61.7) * (3.55)^2)/.545
    F=1426.74 N or 1.42674 kN
    I know this is right for part a, I just don't understand what they are asking for part b or what equation to use. I would appreciate any help.
     
    Last edited: Feb 12, 2008
  2. jcsd
  3. Feb 13, 2008 #2
    Please help...I just need to figure out how I would start this. I understand now that the "tension" is the force that I calculated in (a) but I am unsure how to find the ratio of this tension to her weight (61.7 kg) i was thinking just diving 61.7/1.42674 but that does not seem right. I would greatly appreciate any help.
     
  4. Feb 13, 2008 #3
    Got it...thanks anyway....--->1426.74/(61.7 * 9.81)=2.3572
     
  5. Feb 13, 2008 #4

    rl.bhat

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    Homework Helper

    Ratio is f/mg
     
    Last edited: Feb 13, 2008
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