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Non-ideal atwood machine problem

  1. Jan 23, 2008 #1
    [SOLVED] non-ideal atwood machine problem

    1. The problem statement, all variables and given/known data
    Atwood machine.
    mass a is 19kg and mass b is 9 kg
    the pulley itself has diameter of 15cm and mass of 41kg
    mass A and b are release from rest. How far does mass A move in 2 sec?

    2. Relevant equations

    I = 1/2 mr^2

    3. The attempt at a solution
  2. jcsd
  3. Jan 23, 2008 #2
    really stuck at this non-ideal pulley problem..please help due tomorrow
  4. Jan 23, 2008 #3
    I came up with two equation, but not sure if it is correct:
    Ta(0.0075) + Tb(0.0075) = 1/2mr^2a
    Total energy= 1/2mv^2 +1/2W^2+ mgh
    What shall I do first? Find the acceleration of the two objects?
  5. Jan 23, 2008 #4
    really need help in this
  6. Jan 23, 2008 #5

    Doc Al

    User Avatar

    Staff: Mentor

    To find the acceleration, analyze the situation using Newton's second law, not conservation of energy.

    You'll need three equations: one for mass a, one for mass b, and one for the pulley.

    Analyze the forces on each object separately and apply Newton's 2nd law. Combine those three equations to solve for the acceleration.
  7. Jan 23, 2008 #6
    ohh alright thanks!
  8. Jan 23, 2008 #7
    wait, equation for what? solving for acceleration?
    so i find 3 equations of acceleration for mass a, b and pulley?
  9. Jan 23, 2008 #8
    first i guess all the acceleration is the same for pulley, mass A, and Mass B
    i set them equal to each other and solve for acceleration

    so the accleration is 2.02m/s^2
  10. Jan 23, 2008 #9

    Doc Al

    User Avatar

    Staff: Mentor

    Looks about right.
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