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Homework Help: A small ball of mass M

  1. Mar 2, 2005 #1


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    A small ball of mass M is attached t two identical springs of constant k, which are attached to the floor and the roof. The springs have unstretched lengh L/2. At what position will the ball remain at rest?

    The back of the book gives the answer.
    [tex]\frac{1}{2}L(1+\frac {Mg}{kL})[/tex]

    But the text doesn't do a good job explaining how to arrive at that answer. I've stared at it for 20 minutes. Any thoughts?
  2. jcsd
  3. Mar 2, 2005 #2

    Doc Al

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    When the ball is exactly in the middle (at L/2) what forces do the springs exert on it? And at a point a distance X beneath that middle point? What does X have to be so that the net spring force balances the ball's weight?
  4. Mar 2, 2005 #3


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    Okay draw the forces...Apply Newton's second law.And then use the fact that the body is equilibrium.

    The answer in the book gives the body-ceiling distance...

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