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Homework Help: Ball tied to string- centripetal force

  1. Mar 26, 2009 #1
    1. The problem statement, all variables and given/known data

    A ball, mass m = 1.5 kg is twirled at constant speed v at the end of a massless string in a vertical circle of radius r = 1.2 m. The period for this uniform circular motion is T = 1.3 s. Free body diagrams for the ball at the top and at the bottom of the circle are shown.
    a. Compute the speed v of the ball.
    b. Compute the ball’s centripetal acceleration.
    c. Compute the “centripetal force” on the ball.
    d. When the ball is at the top (point A in the figure) compute the tension FTA in the string.
    e. When the ball is at the bottom (point B in the figure) compute the tension FTB in the string.

    2. Relevant equations

    I understand all the parts except for question c, is the formula for centripetal force m*(v^2/r)? Or is it the same as the The tension in the string?
  2. jcsd
  3. Mar 26, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    No, they are not the same.
  4. Mar 26, 2009 #3
    thanks a lot Doc!
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