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Homework Help: Acceleration with friction

  1. Oct 18, 2007 #1
    1. The problem statement, all variables and given/known data
    Two blocks of wieghts 3.6N and 7.2N are connected by a massless string and slide down a 30 degree inclined plane. The coefficient of kinetic friction b/t the lighter block and the plane is 0.10, that b/t the heavier block and the plane is 0.20. Assuming the lighter block leads, find magnitude of acceleration of the blocks.

    2. Relevant equations


    3. The attempt at a solution

    I dunno, I just guessed at the above equations. Anyway, I'm pretty stuck on this problem (meaning I don't even know where to begin). It's the fact that the question didn't give any forces that threw me off, they just gave masses (and in N too).
  2. jcsd
  3. Oct 18, 2007 #2
    The force causing them to slide will be the force due to gravity.

    F = ma -> F = mg
  4. Oct 18, 2007 #3
    Well, yeah, I thought of that, but wouldn't that just be the force in the y direction? Like, shouldn't there also be a force in the x direction, since it's on an inclined plane and all? That's the acceleration I'm having trouble finding. See, it's that that I was guessing at in the above equations.

    Oh, and since they're connected on a string, wouldn't F=mg be Fy=T-mg, since there's supposedly some tension in the string as well?
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