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Homework Help: Newton's Laws: Equilibrium

  1. Jul 20, 2007 #1
    1. The problem statement, all variables and given/known data
    A tether ball leans against the post to which it is attached. If the string to which the ball is attached is 1.80m long, the ball has a radius of .200m, and the ball has a mass of .500kg, what are the tension in the rope and the force the pole exerts on the ball? assume that there is so little friction between the ball and the pole that it can be neglected. ( The string is attached to the ball such that a line along the string passes through the center of the ball.)

    2. Relevant equations
    [tex]F_{x} = 0[/tex]
    [tex]F_{y} = 0 [/tex]

    3. The attempt at a solution
    Part I
    Required: tension on the rope
    T = ??
    wball = (.500kg)(9.8m/s^2) = 4.9N
    [tex]\sum{F_{y}} = 0 = T\cos{\theta} + (-w_{ball})[/tex]
    [tex]T = \frac{4.9N}{\cos{\theta}}[/tex]
    *I computed theta using its distances:
    sin(theta) = x_{radius} / h_{tension}
    = arcsin {0.200m/1.80m}
    = 6.38 degress
    [tex]T = \frac{4.9N}{\cos{6.38}}[/tex]

    T =4.93N

    Part II
    reqd: force on pole on ball:
    F_{pole on ball} = ?
    \sum{F_{x}} = 0 = T\sin{\theta} - F_{p.on.B}
    (4.93N)sin{6.38} = F_{pole on ball}
    F = .548N?
    Last edited: Jul 20, 2007
  2. jcsd
  3. Jul 21, 2007 #2


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    Homework Helper

    You've got both answers correct.
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