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Newton's Laws of Motion : Block Problem

  1. Jan 10, 2014 #1
    1. The problem statement, all variables and given/known data

    In the arrangement shown, all surfaces are frictionless, mass of block M = 30 kg and m = 20 kg.
    If F = 180 N , Find accelerations of both the blocks
    attachment.php?attachmentid=65490&stc=1&d=1389379517.jpg

    2. Doubt

    What amt of force will act on larger block M, just T(coz of horizontal string around the pulley) or 2T(coz of both the strings around the pulley)
     

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  2. jcsd
  3. Jan 10, 2014 #2
    Imagine that the pulleys were not attached to anything else except the string. In which directions do you think they would be pulled?
     
  4. Jan 10, 2014 #3

    tiny-tim

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    hi rajumahtora! :smile:

    when you consider the forces on a body, you must consider the whole body …

    the block M is attached to the pulleys, so you must consider the external forces on the block-plus-pulleys :wink:
     
  5. Jan 11, 2014 #4

    tiny-tim

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    (please don't start a new thread)

    as i said before, so you must consider the external forces on the block-plus-pulleys (as a single body), not just the block on its own
     
  6. Jan 11, 2014 #5

    haruspex

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    rajumahtora, please clarify your question. There are two pulleys attached to M. Are you asking what the net force on M is from the two pulleys, or what force each pulley exerts on the block separately?
    (What do you think the two separate forces are?)
     
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