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The laws of motion-a block pulled by a light cord

  1. Dec 27, 2013 #1
    1. The problem statement, all variables and given/known data
    A block of mass 2.20 kg is accelerated across a rough surface by a light cord passing over a small pulley as shown in figure.The tension T in the cord is maintained at 10.0N,and the pulley is 0.100m above the top of the block.The coefficient of kinetic friction is 0.400m.
    Determine the acceleration of the block when x=0.400.

    2. Relevant equations



    3. The attempt at a solution
    Are there any mistake?
    tanθ=0.4/0.1
    θ=76.0°
    F-f=ma
    10sinθ-0.4x(2.2x9.8-0.1cosθ)2.2a
     

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    Last edited: Dec 27, 2013
  2. jcsd
  3. Dec 27, 2013 #2

    NascentOxygen

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    Staff: Mentor

    It is a mistake to present a problem like this without an accompanying diagram, and a mistake to attempt to solve it without drawing a forces diagram to help you.

    You also haven't indicated the tension in the cord.

    http://imageshack.us/scaled/landing/109/holly1756.gif [Broken]
     
    Last edited by a moderator: May 6, 2017
  4. Dec 27, 2013 #3
    Sorry.:shy:
     
    Last edited by a moderator: May 6, 2017
  5. Dec 27, 2013 #4

    NascentOxygen

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    Staff: Mentor

    Okay, third mistake, you have attached the wrong pic!
     
  6. Dec 27, 2013 #5
    Sorry again.
     
  7. Dec 27, 2013 #6

    tiny-tim

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    hi haha1234! :smile:

    what is this? :confused:
     
  8. Dec 27, 2013 #7
    (2.2x9.8-0.1cosθ) is the normal force of the block.
     
  9. Dec 27, 2013 #8

    tiny-tim

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    but 0.1cosθ isn't a force, it's a distance :confused:
     
  10. Dec 27, 2013 #9
    Oh,i have made a stupid mistake.
    I can find the correct answer now.
    Thank you!
     
  11. Dec 27, 2013 #10
    deleted
     
    Last edited: Dec 27, 2013
  12. Mar 14, 2016 #11
    tanθ=0.1/0.4 <- check it.
     
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