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Relationship of acceleration in two-pulley system

  1. Feb 4, 2015 #1
    1. The problem statement, all variables and given/known data
    upload_2015-2-4_20-24-52.png
    What is the relationship between a1 and a2
    A.a1=a2
    B.a1=2a2
    C.a2=2a1
    D.a1=a2√2
    E.a2=a1√2
    F.There is no simple relationship between the two acceleration
    2. Relevant equations
    a = F/m

    3. The attempt at a solution
    I am quite confused with the second pulley , so the weight of m2 is divided to 2 tension through the second pulley , but i cant find what is the magnitude of the upper tension ,therefore we cant find the lower tension or the acceleration either.
    So i choose F as my answer , however i am not sure . Is my answer right ?.
     
    Last edited: Feb 4, 2015
  2. jcsd
  3. Feb 4, 2015 #2

    DEvens

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    Conserve string.
     
  4. Feb 4, 2015 #3
    sorry i dont get it . can you be more specific , and which answer do you choose :D
     
  5. Feb 4, 2015 #4

    DEvens

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    Really? That's not enough?

    Ok. When mass m1 moves a distance of 1 unit, how far must the mass m2 move?
     
  6. Feb 4, 2015 #5
    That's where i was confused.
    If m2 goes a distance of x. Will m1 goes a distance of x/2 or 2x?
     
  7. Feb 4, 2015 #6

    haruspex

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    Let the lengths of the horizontal portions be x (on the left), y (top right), z (lower right).
    What equations relate them?
     
  8. Feb 9, 2015 #7
    I have the same problem too
    I think that it is Δx = Δy + Δz
    Since Δy is the same as Δz, so Δx = 2Δy = 2Δz
    So, a2 = 2a1, right ?
     
  9. Feb 9, 2015 #8

    BvU

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    Try again.
     
  10. Feb 9, 2015 #9
    Hmm..
    I tried and got the same answer, a2 = 2a1
    Please explain the correct answer to me

    EDIT :
    Tried again and get a1 = 2a2
     
    Last edited: Feb 9, 2015
  11. Feb 9, 2015 #10

    haruspex

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    Good.
     
  12. Feb 24, 2015 #11
    sr i didnt understand , since S = 1/2 at^2
    then if Δx=2Δy .
    then ax should be equal 2 ay ?
    then a2 = 2a1 ?
     
  13. Feb 24, 2015 #12

    haruspex

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    That's irrelevant to how the lengths x, y and z relate.
    It isn't.
    What combinations of lengths x, y and z are known to be constant?
     
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