1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Free body diagram of atwood machine

  1. Jun 21, 2011 #1
    1. The problem statement, all variables and given/known data

    I need to find the forces on this modified atwood machine:


    3. The attempt at a solution

    What I think:

    - On mass M there are two forces, Mg and -T.
    - On the mass above the spring there are two more forces, -2mg and T.
    - On the mass below the spring there are also two forces, -mg and kx.

    Is any of this correct?
  2. jcsd
  3. Jun 22, 2011 #2
    You seem to have got it right.
  4. Jun 22, 2011 #3
  5. Jun 22, 2011 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Careful: The only force of gravity on that mass is mg. (But there's a spring force on it.) So there are three forces acting on that mass.
  6. Jun 22, 2011 #5
    Ooh, you're right, I was thinking there might be a 2mg plus a kx after you mentioned the spring force, but I think it's only mg and kx.

    I knew the spring was going to make it trickier than I had thought.
  7. Jun 22, 2011 #6
    Are the forces on the mass above the spring then T and -mg and - kx?
  8. Jun 22, 2011 #7

    Doc Al

    User Avatar

    Staff: Mentor

  9. Jun 22, 2011 #8
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Free body diagram of atwood machine
  1. Free body diagram (Replies: 4)

  2. Free body diagram help (Replies: 8)