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How to find mass in an Atwood machine

  1. Oct 7, 2015 #1
    1. The problem statement, all variables and given/known data

    A pumpkin and a weight are attached to a frictionless pulley. As the 5kg weight is released, the pumpkin accelerates down at 4.65 m/s^2 to the ground. What is the mass of the pumpkin?



    2. Relevant equations

    How do I find the mass?
    3. The attempt at a solution

    T=m1g
    ma=m2g-T
    m=m2g-T/a
    m=m2g-49/4.65
    m=10.53-m2g
    m-10.53=m2g
    10.53+5=15.53
    m2=1.57kg
     
  2. jcsd
  3. Oct 7, 2015 #2

    haruspex

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    It says the pumpkin accelerates downwards. Does that make it more or less than 5kg?
     
  4. Oct 20, 2015 #3
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  5. Oct 20, 2015 #4

    haruspex

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    You don't make it clear, but I assume you are using m ( or m1) for the mass of the weight and m2 for the pumpkin.
    If T is the tension in the rope, what are the forces acting on the pumpkin? What "F=ma" equation does that give you? Same questions for the weight.
     
  6. Feb 14, 2016 #5
    I think your formula is off.

    Shouldn't it be m2 = (ma + T) / g ?
     
  7. Feb 14, 2016 #6

    haruspex

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    How is that different from
    ?
     
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