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Homework Help: Blocks on a Ramp Question

  1. Sep 30, 2007 #1
    1. The problem statement, all variables and given/known data
    In Fig. 6-48, block 1 of mass 1.8 kg and block 2 of mass 2.9 kg are connected by a string of negligible mass and are initially held in place. Block 2 is on a frictionless surface tilted at = 38o. The coefficient of kinetic friction between block 1 and the horizontal surface is 0.20. The pulley has negligible mass and friction. Once they are released, the blocks move. What then is the tension in the string?
    **image attached**

    2. Relevant equations
    For m1, fxnet=Uk(FN)-T=ma and fynet=FN-mg=0 and for m2, fxnet=T-mgsin(theta)=ma and fynet=FN-mgcos(theta)=0... I don't know if these are correct or not, that's what I got when I did the free body diagrams.


    3. The attempt at a solution
    I don't really know how to go about solving this problem... should I add any two equations together in order to get T?
     

    Attached Files:

  2. jcsd
  3. Sep 30, 2007 #2

    Chi Meson

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    Homework Helper

    As a shortcut, use a tilted frame of reference for m2. Instead of x and y, consider the forces that are parallel and perpendicular to the surface. The force down the slope is a component of the gravitational force (on m2). The tension acts up the slope.

    The net force on this system ends up being (the down-slope component of gravitational force on m2) - (frictional force on m1)
     
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