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Finding acceleration and tension using Newton's laws

  1. Feb 18, 2013 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations

    Newton's laws of motion.

    3. The attempt at a solution

    I split up the entire thing into two pieces.


    The left diagram illustrates the left block of 3 kg. I set the x-axis parallel to the ramp. The right is of the right block, where the x-axis is taken to be parallel to the horizontal surface.

    Since accelerations occurs on the system,

    By the left illustration,
    ƩFx = T - w1sin30 = m1a

    and by the right illustration,
    ƩFx = Fcos20 - T = m2a

    I can substitute the masses by their respective quantities, but my problem is that I have three unknowns (T, F, and a) and only two equations. I also don't really see how using the vertical components of motion will help me out.

    Also, one thing I'm not even completely sure about is whether it's even correct to assume that tension is the same on both sides of the rope.

    What am I doing wrong in here?
  2. jcsd
  3. Feb 18, 2013 #2

    Doc Al

    User Avatar

    Staff: Mentor

    F is given. Look at the diagram.

    For a massless rope, that is a good assumption.
  4. Feb 18, 2013 #3
    Okay I think it's time to take a break then...

    Thanks for the help.
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