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Force of the rotating ball

  1. May 23, 2012 #1


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    I have a question about force produced by rotating ball.
    Let's say the ball rotates clockwise.
    The rotating ball is attached to the rotation axis with a rigid rod.
    The rotating ball is placed inside of the box.
    The box is placed on the very sensitive scale.
    The box is vibrating.
    I would like to know the direction of the force F exerted on the box at each of the following ball positions:
    Ball is a 12 o'clock
    Ball is a 3 o'clock
    Ball is a 6 o'clock
    Ball is a 9 o'clock

    What would scale show in terms of direction of force F for each of the above positions?

  2. jcsd
  3. May 24, 2012 #2


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    Your question is not entirely clear. I'll make these assumptions:
    The axle of rotation is fixed to the box.
    Some mechanism is forcing the ball to rotate around the axle at constant rate.
    The vibration is a result of this, not of any additional forces.
    The rotation is in the vertical plane.

    Ignoring gravity, the force exerted by the ball on the axle (and thence on the box) is the reaction to the centripetal force. At 12 o'clock the force is upwards, at 3 o'clock to the left, etc. Just add the gravitational force for the total.
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