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Homework Help: Tension in cord at 30.0 degrees

  1. Aug 8, 2012 #1
    1. The problem statement, all variables and given/known data
    A 0.160 kg ball attached to a light cord is swung in a vertical circle with a radius of 70.0 cm. At the top of the swing, the speed of the ball is 3.26 m/s. The center of the circle is 1.50 m above the floor.

    Determine the magnitude of the tension in the cord when the cord is 30.0 degrees below the horizontal.

    m= 0.160 kg
    r = 70.0 cm or 0.700 m
    v = 3.26 m/s
    v (30.0 degrees) = 5.59 m/s
    d = 1.50 m

    2. Relevant equations
    T = mv^2/r + mgsin(degree)

    3. The attempt at a solution
    T = mv^2/r = mgsin(degree)
    = (0.160 kg)(5.59m/s)^2 / 0.700 m + (0.160 kg)(9.81 m/s^2)(Sin30)
    = 7.922765714

    May need to double check the velocity I used here....

    Thank you
  2. jcsd
  3. Aug 8, 2012 #2


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    Look's ok to me. How many significant figures should you retain in the answer?
  4. Aug 8, 2012 #3
    To me it is conservation of energy that determine the speed at other point compare to top of the loop.
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