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Homework Help: 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

    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


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    Homework Helper

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