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Homework Help: Quick Question

  1. Sep 27, 2007 #1
    1. The problem statement, all variables and given/known data
    A 12.0-kg box resting on a horizontal, frictionless surface is attached to a 5.00- kgweight by a thin, light wire that passes over a frictionless pulley. The pulley has the shape of a uniform solid disk of mass 2.50 kg and diameter 0.440m .

    What are the x and y components of the force that the axle exerts on the pulley?
    2. Relevant equations
    Ok, so I found the tension in the Horizontal Wire to be 32.2
    Ok, then I found the tension in the Vertical Wire to be 35.6
    The acceleration of the box when it goes down is 2.68 m/s^2

    3. The attempt at a solution

    So, I asked the teacher and the teacher told us that the x component is the tension in the horizontal wire and the y component is the vertical tension plus the weight of the block that is accelerating downwards. So, I did that. The x component would be 32.2 and the y component woud be 35.6 + mg which is 84.6. I tried that but that is not the answer. I think that the x component is right but I am messing up somewhere on the y component. Can anyone help me with this one. Thanks in advance.
  2. jcsd
  3. Sep 27, 2007 #2


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    The acceleration would also be the angular acceleration of the pulley times its diameter, and that times its mass would be the force on the pulley, I think. So calculate the vertical and horizontal components of the acceleration vector on the pulley, remembering all the while that only the tensions would act on the pulley because all forces on the pulley are transmitted through the wires.
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