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Homework Help: Not sure how to do 2 body problem

  1. Feb 26, 2012 #1
    1. The problem statement, all variables and given/known data
    Look below for diagram

    Mass m1is on an inclined plane and weighs 1.00 kg. The inclined plane creates a 40.0 degree angle with the ground, and μk = 0.225. Mass m11 is attached to a weight hanging off the edge via pulley, called M2. M2 has a mass of 1.50kg and hangs from a height h of 50.0 cm. When the system is released from rest, how long will it take M2 to hit the floor? Assume the static frction is exceeded by the weight of M2

    2. Relevant equations
    f=ma (or f = mg)
    f1 = MgSin∅
    f2 = mg
    a = net force/net weight
    a = (m2g-m1gsin∅)/(m1+m2) - not sure how this was derived, was in my book

    3. The attempt at a solution
    a=(1.5 kg ) (9.8 m/s2)-(1 kg ) (9.8 m/s2) sin(40)
    (1 kg )+(1.5 kg )

    This solution feels wrong and I'm very sure I did it wrong. Please look it over for me; I'm terribly confused by this problem.

    Attached Files:

    Last edited: Feb 27, 2012
  2. jcsd
  3. Feb 27, 2012 #2
    Sorry for bumping but still looking for help on this
  4. Feb 27, 2012 #3


    User Avatar

    Staff: Mentor

    What happened to the dynamic friction between the first mass and the ramp?

    List all the forces acting on the individual masses, then draw a Free Body Diagram for each. From that you should be able to write equations pertaining to each body and solve for their shared acceleration.
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