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Connected Objects

  1. Sep 29, 2009 #1
    1. The problem statement, all variables and given/known data
    Two blocks are connected by a string, as shown in the figure . The smooth inclined surface makes an angle of 35degrees with the horizontal, and the block on the incline has a mass of 5.7kg. The mass of the hanging block is m = 2.8 kg. Find the magnitude of the hanging block's acceleration.


    2. Relevant equations
    a=m(hanging)g-Fg(plane)sintheta+m(plane)gcostheta/m(both)


    3. The attempt at a solution
    a=(9.8m/s^2)[2.8kg-(5.7kg*sin35degrees)+(5.7kg*cos35degrees)]/(5.7kg+2.8kg)
     
  2. jcsd
  3. Sep 29, 2009 #2

    kuruman

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    Homework Helper
    Gold Member

    I don't know where you got the equation that you say is relevant, but it doesn't look right.

    You need to draw two free body diagrams, one for each mass. Add all the forces vectorially in each free body diagram. This gives you the net force acting on each mass. Set the net force equal to mass times acceleration. You will end up with two equations and two unknowns. The unknowns are the tension T and the acceleration a. Solve for the tension in terms of a in one of the equations. Put that in the second equation to get a.
     
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