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Fletcher's Trolley (Hanging Mass Problem)

  1. Apr 5, 2014 #1
    1. The problem statement, all variables and given/known data
    A 1.20kg object is placed on a smoothe level table and is attached to a hanging mass using a light string over frictionless pulley in a Fletcher's trolley arrangement. The 1.20kg object accelerates along the table at 2.31m/s^2 while the hanging object accelerates down at the same rate. Determine the

    a. Mass of the hanging object

    b. tension in the string

    3. The attempt at a solution

    I drew 2 FBDs with the forces acting on each individual mass.

    We know that Fapp = Fg2 = T

    What I can't figure out is a formula that rearranges the variables to find m2

    For example, I know that a = F/∑m

    But we don't know what ∑m is.

    We could relate Fapp to Fg2, but to do that we'd need to know m2

    We can relate T to Fapp or Fg2, but we'd need to know m2...

    You can see my dilemma. I've tried a good 10 different formulas, and now I'm just spitballing. I have no idea how I am supposed to create a formula that tells us m2 without knowing F

    Please help.
  2. jcsd
  3. Apr 5, 2014 #2
    Care to share your FBD's?
  4. Apr 5, 2014 #3
    Actually, I had a friend help me. Thanks anyways though. It turns out I was forgetting to factor in Fnet (the masses are moving). Fnet would have had me using a formula like this.

    m2a = m2g - m1a

    And solving from there.

    It's very clear I need to remember that T ≠ Fg/2 while it is moving, but that T = Fapp

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