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Homework Help: Force and motion

  1. May 19, 2008 #1
    1. The problem statement, all variables and given/known data
    Two blocks rest on slopes and are coonected by a pulley. The left hand slope makes a 60 degree ngla with the horizontal. The right hand slope makes a 20 degree angle. How should the masses compare if the objects do not slide along the frictionless slopes? Book answer is that right hand mass is 2.5 times the left hand mass.

    2. Relevant equations
    F = ma

    3. The attempt at a solution

    For the left-hand mass T + Flg + Nleft = 0

    For the right-hand mass T + Frg + N right = 0

    Coordinates y is vertical and x is horizontal

    Solving for the y components in the left hand mass:

    Mlg sin 30 degrees + T sin 60 degrees - Mlg = 0

    T = 0.5 Mlg/0.866

    Solving for the y components in the right-hand mass:

    T sin20 degrees - Mrg + Mrg sin 70 degrees = 0

    T = 0.06 Mrg/ 0.342

    Equating the two Ts, Mr = 0.5 Ml (0.342)/ (0.866)(0.06) = 3.3
  2. jcsd
  3. May 19, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    I'm having a hard time following what you did. Hint: Consider force components parallel to the inclines.
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