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Homework Help: 2 blocks, 1 pulley

  1. Oct 2, 2005 #1
    This is a no number one :S

    A block with mass m1 is placed on an inclined plane with slope angle theta and is connected to a second hanging block with mass m2 by a cord passing over a small frictionless pulley. The coefficient of static friction is mu s and kinetic is mu k.

    a) Find the mass m2 for which the block m1 moves up the plane at a constant speed once it is set in motion.

    b) Find the mass m2 for which block m1 moves down the plane at constant speed once it is set in motion.

    c) For what range of values of m2 will the blocks remain at rest if they are released from rest?

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    Last edited: Oct 2, 2005
  2. jcsd
  3. Oct 2, 2005 #2


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    What have you tried? What are the relevant equations? Did you construct a free body diagram?
  4. Oct 2, 2005 #3
    Well, m2 would have 2 forces acting on it I suppose (gravity and tension); while m1 has components with mu s and mu k. For m1 to move at constant speed, I guess Fnet = Ma (a=0) thus Fnet = 0

    I'm lost after this point :s
  5. Oct 2, 2005 #4


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    The tension in the rope holding back m2 also pulls forward m1.
  6. Oct 2, 2005 #5
    ah yes, should the 2 tensions cancel out?
  7. Oct 2, 2005 #6


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    They will Eventually.

    You can make up two eqns of motion for each mass where each one involves the tension T. Then eliminate T from the two eqns.
  8. Oct 2, 2005 #7
    I think I asked you the same question Fermat. Hey are we alowed to help.
  9. Oct 2, 2005 #8
    Sure, you can help me :)
  10. Oct 3, 2005 #9


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    Yes, I think I remember that one.

    Anyone can help, but you should read the sticky at the top of this forum (and others)
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