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Homework Help: Tension problem

  1. Oct 18, 2004 #1
    Everyone I know is having problems with this question:

    3. [PSE6 6.P.011.] A 3.85 kg object is attached to a vertical rod by two strings as in Figure P6.11. The object rotates in a horizontal circle at constant speed 7.30 m/s.

    Figure P6.11

    (a) Find the tension in the upper string.
    (b) Find the tension in the lower string.

    http://www.webassign.net/pse/p6-11.gif for the figure

    I've tried using various force equations, only to be wrong. Does anybody know how to do this problem??
  2. jcsd
  3. Oct 18, 2004 #2
    Anybody know how to do this problem? Tried a lot of things, but I'm down to my last chance to answer the question correctly
  4. Oct 18, 2004 #3
    it seems you are desparate, just show me your "force equation and I help you out right know
  5. Oct 18, 2004 #4
    Well I tried some forms of the centripetal acceleration formula for the upper tension, and I also tried 3.85*9.88(cos of the angle) + 1/2 the horizontal force, but they haven't worked out.
  6. Oct 18, 2004 #5
    Only because you try to do something, I'm going to help.
    Use these forces ==>
    T"sin(alpha)-T'sin(alpha)-mg=0 and T"cos(alpha)+T'cos(alpha)=mv^2/r
    where T" is the upper tension and T' is the lower tension. Also, if you want to find
    cos(alpha) and sin(alpha) use your sketch
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