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Homework Help: Not sure about my solution (fictionless Pulley)

  1. Dec 7, 2006 #1
    Masses m and 2m hang from opposite ends of a string passing over a light,
    frictionless pulley. What is their acceleration?




    I said that the total unblalance force on the two objects is 2mg-mg=mg and the total mass is 2m+m=3m

    So the acceleration a is a=mg/3m=g/3

    Is this right? could somebody check it for me please? thanks :redface:
     
  2. jcsd
  3. Dec 7, 2006 #2

    Doc Al

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    Staff: Mentor

    You are correct. But why not check it yourself, by using a more general method: Set up force equations (Newton's 2nd law) for each mass separately and combine the two equations. That will allow you to solve for both the acceleration and the string tension.
     
  4. Dec 7, 2006 #3
    Ok that makes sense ^_^ I'll try it. thanks again
     
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