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Homework Help: Ball in Vertical Circle on End of String, Tangential and Radial Acceleration

  1. Sep 17, 2010 #1
    1. The problem statement, all variables and given/known data

    A ball swings in a vertical circle at the end of a rope 1.30 m long. When the ball is 36.1° past the lowest point on its way up, its total acceleration is (-22.5 i + 20.2 j) m/s2.

    (a) Determine the magnitude of its radial acceleration.

    (b) Determine the speed and velocity of the ball.

    2. Relevant equations

    A = v^2/r
    Ar = Atotal - Atangential

    3. The attempt at a solution

    I have no idea where to go with this. I am stuck on the first part. My issue is in figuring out the tangential acceleration so that I can subtract that from the total acceleration to find the radial/centripetal acceleration. My thought is that tangential acceleration should be zero, because the ball is swinging on the end of a string, and its speed should not be changing, only its velocity.
  2. jcsd
  3. Sep 17, 2010 #2


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    Homework Helper

    You have a=(-22.5 i + 20.2 j) m/s2. The acceleration vector is made up of the sum of the radial and tangential acceleration. Using your coordinate system, the j vector points up or towards the center of rotation right? So the radial acceleration is?
  4. Sep 17, 2010 #3
    no, up is not towards the center of rotation. it is 36.1 degrees past the bottom
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