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Inclined Pulley problem

  1. Oct 8, 2013 #1
    1. The problem statement, all variables and given/known data

    m1 has a mass of 47 kg and m2 has a mass of 35 kg. the coefficient of friction between m1 and the surface of the inclined plane are us=.42 and uk=.19 m1 is on an inclined plane angled 25 degrees

    A) if the masses are held in place and then released, will they start to move?
    B) what mass would you have to add to m2 to cause the masses to begin to move?
    C) what would be the acceleration of the masses after adding the additional mass?

    2. Relevant equations
    For a- I know the answer is no
    For b- made fnet equal to 0 and solved for m2. (37.8) subtracted 37.8 from 35 to get 2.8kg of additional mass

    3. The attempt at a solution
    For c- I used fnet=ma fnet= -Ff-fparallel+m2g/m1+m2
    However I didn't get the right answer which is supposed to be 5.7 m/s2 ..
    What am I doing wrong??
  2. jcsd
  3. Oct 8, 2013 #2


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    Gold Member

    It's not clear what is going on. How are two masses connected ( if they are ), and where is m2 ?
  4. Oct 9, 2013 #3
    M2 is suspended in the air m1 is on an incline, connected together by a pulley
  5. Oct 9, 2013 #4


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    Staff: Mentor

    Could be a typo in the question. Suppose for a moment that all surfaces were without friction. What would the acceleration be then? Is your expected "right answer" achievable?
  6. Oct 19, 2013 #5
    I have no idea how they got tht answer.. How would you go about solving that?
  7. Oct 19, 2013 #6


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    Staff: Mentor

    Start with the free body diagrams, of course.
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