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Homework Help: Equations of Motion

  1. Feb 11, 2013 #1
    1. The problem statement, all variables and given/known data

    I seem to be having trouble setting up my equations and not getting the correct answer to some of these problems.

    Ex 1:
    Determine the acceleration of block A when the system is released. The coefficient of friction and the weight of each block are indicated in the figure. Neglect the mass of the pulleys and cords. See attached image.

    2. Relevant equations

    m = [itex]\frac{lb}{32.2}[/itex]

    So for my first set of equations on block A:
    ƩFx = 2T+ μmgcos60° - mgsin60° = ([itex]\frac{lb}{32.2}[/itex])aA

    ƩFy = N - mgcos60° = 0
    N = mgcos60°

    Ff = μ*N = μmgcos60°

    Block B:
    ƩFy = T - mg = ([itex]\frac{lb}{32.2}[/itex])aB

    aB = -2aA

    1. Are my equations correct?
    2. Was I correct to use 60°? (I'm sure it is right but....I feel a bit doubtful.)

    Attached Files:

  2. jcsd
  3. Feb 11, 2013 #2


    User Avatar
    Homework Helper

    Look at the picture. The angle is 30°.

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