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Atwood's machine problem

  1. Sep 6, 2003 #1
    Okay, I had to do a problem concerning the Atwoods machine over the weekend. I'm not doing very well in Physics right now, and I don't have any friends in that class, so I thankfully found this place. I have already tried thinking about these problems...

    1. If two objects of equal mass are suspended from either end of a string passing over a light pulley (an Atwood's machine), what lind of motion do you expect to occur? Why?

    I said that if the two objects of equal masss are suspended over a light pulley, the objects will move only until they are both at wqual distances from the ground. Then they will not move at all.

    But the part I'm stuck on is -- why? Why does this occur? How can I explain this correctly?

    2. For an Atwood's machine, how would you expect the acceleration to change if you:

    - Move mass from one side to the other, keeping the total mass constant?

    I'm not sure if this is correct: I said, the acceleration would increase. The mass of one side is gerater than the mass of the other, meaning the heaver side has a greater weight force (mg) acting upon it equating to a greater accelearation.

    - How about if you gradually increase the mass of both sides, keeping the difference in mass constant?
    I said the acceleration will remain the same because ratio of masses are equal. I am not sure if this is correct either.

    3. Why do the two masses have the same acceleration?
    I said the two masses have the same acceleration because the tension throughout the string is equal. The combined mass pulls each other at the same rate becauseb oth have the same foreces acting upon them.

    I'm not sure at all if any of my answers are correct. What I need the most help on is #1. If somebody could help me, I would appreciate it very much.
  2. jcsd
  3. Sep 6, 2003 #2


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    Please do not post the same question on two different forums.
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