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Angular momentum and tension of string

  1. Oct 31, 2004 #1
    This problem is baffling me.

    A 3kg puck revolves in a circle on a frictionless table at the end of a 50cm long string. The puck's angular momentum is 3kg (m^2/s). What is the tension in the string?

    This what I did
    L= mrv
    therefore
    3kg*.25m*v = 3kgm^2/2
    v=4m/s
    F=(mv^2)/r
    (3kg*16m/s)/(.25m) = 192N

    is this right?
     
  2. jcsd
  3. Oct 31, 2004 #2

    arildno

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    Dearly Missed

    r should be 0.50 m, not 0.25.
     
  4. Oct 31, 2004 #3
    I agree with arildno, the string is acting as the radius of the circle itself, not as the diameter :smile:
     
  5. Oct 31, 2004 #4

    Doc Al

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