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Block Attached to Pulley Question

  1. Sep 9, 2010 #1
    1. The problem statement, all variables and given/known data

    A 20-kg block with a pulley attached slides along a frictionless ledge. It is connected by a massless string through another pulley to a 5.0-kg block which hangs off the ledge. Find (a) the acceleration of each block, and (b) the tension in the connecting string.

    2. Relevant equations
    FNET=ma



    3. The attempt at a solution
    I set up both free body diagrams with the x axes aligned with the direction of acceleration for each block. I then solved FNET X=max for each block, and acquired the tension (39.2 N) and acceleration (1.96 m/s2). My answer worked algebraically, but according to the answer in my book I made the misassumption that the two blocks had equal magnitudes of acceleration.

    I attempted to solve the problem without assuming equal accelerations, and I ended up with two equations and three variables (T, ax1, and ax2) which I couldn't solve. According to my book, the answer for part (a) is 5.0 cm (?), and part (b) is a20=2.5m/s2, while a5=T=25N. I have had no luck at replicating or making any sense of these answers whatsoever. Thanks in advance for the help!
     
  2. jcsd
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