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Homework Help: Circuler motion angle

  1. Feb 5, 2010 #1
    can some one please tell me where am i wrong?

    A mass of 9.50 kg is suspended from a 1.19 m long string. It revolves in a horizontal circle.
    The tangential speed of the mass is 2.28 m/s. Calculate the angle between the string and the vertical.

    so what i need is the ratio between radius and string length. to find the radius i use v and the fact it equals wr. w is the square of ration between g and l.

  2. jcsd
  3. Feb 5, 2010 #2
    Let the angle between the string and the vertical be [itex]\theta[/itex]

    [itex]Tcos\theta=mg[/itex] ------ (1)

    [itex]Tsin\theta=\frac{mv^2}{r}[/itex] ------ (2)

    Dividing (1) by (2),




    [itex]tan\theta=\frac{v^2}{lsin\theta g}[/itex]






    [itex]cos\theta=0.8[/itex] or [itex]cos\theta=-1.25[/itex]

    Rejecting [itex]cos\theta=-1.25[/itex], we get


  4. Feb 5, 2010 #3


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    I respectfully ask in the future that you do not post full solutions to problems. Provide help and guidance only, per Forum rules. Thanks.
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