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Homework Help: Tension, pulley and acceleration problem

  1. Oct 4, 2007 #1
    1. The problem statement, all variables and given/known data

    In the figure below (part a), two blocks are connected by a lightweight, flexible cord that passes over a frictionless pulley.
    (a) If m1 = 3.3 kg and m2 = 5.1 kg, what are the accelerations of each block?
    (b) What is the tension in the cord?

    2. Relevant equations

    3. The attempt at a solution

    I got the acceleration, a, to be 2.1, which is correct, but I cannot figure out how to get part b. I found the weight in newtons of the 5.1 and 3.3 blocks, and then subtracted and used F=MA to find the acceleration. Can someone point me in the right direction about the tension? Thanks!
  2. jcsd
  3. Oct 4, 2007 #2
    maybe i didnt provide enough info..... i found the weight in newtons for the 5.1kg weight to be 49.98N, and 32.34N for the 3.3kg weight. I subtracted and got 17.64N. I did F=MA, with F being 17.64, m being 8.4 (or 5.1+3.3) and found a to be 2.1. Now I cant seem to find out how to do the tension part.....

    Thanks in advance for the help!
  4. Oct 4, 2007 #3

    Doc Al

    User Avatar

    Staff: Mentor

    In order to find the tension you need to consider each mass separately and apply Newton's 2nd law. It looks like the free body diagrams for each mass are already given--translate them into equations and solve together. (Or, since you have the acceleration, you can just analyze one of the masses.)
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