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Homework Help: Help quickly

  1. Jan 10, 2005 #1
    Help quickly plz

    I need help on this and quick!:
    A 4kg block is pushed alomng the ceiling with a constant apllied force of 85N that acts at an angle of 55 degrees with the horizontal. The block accelerates to the right at 6m/s^2. detremine the coefficient of kinetic friction between the block and the ceiling.

    ok i worked out the problem but i got the wrong answer. the values i got are: for normal force=69.62N. for ap=12.19. for af=6.19. for Ff=24.8N final answer=.356 and i need .816 what did i do wrong?
     
  2. jcsd
  3. Jan 10, 2005 #2

    dextercioby

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    Check the numbers in the text of the problem.That block should be flying...

    Daniel.
     
  4. Jan 10, 2005 #3
    what do u mean the numbers in the problem are right???
     
  5. Jan 10, 2005 #4

    dextercioby

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    1.U double posted.Two threads on the same problem.It's not fair... :grumpy:
    2.Yes,by the looks of it,the normal force should be zero and the body should raise from the ground...

    Daniel.
     
  6. Jan 10, 2005 #5
    Dex, its being pushed agaisnt the ceiling...
     
  7. Jan 10, 2005 #6
    wait but why if someone is pushing it on the ceiling? ur confusing me!
     
  8. Jan 10, 2005 #7
    OOHHHH I know, we forgot to account gravity, get the normal force, subtract or add gravity, im to tired to think, and then divide by Ff!!! see which one works
     
  9. Jan 10, 2005 #8

    dextercioby

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    Sorry,didn't read that part. :mad: You're right...It doesn't fly away...

    Daniel.
     
  10. Jan 10, 2005 #9
    wait what? how do i add or subtract gravity?
     
  11. Jan 10, 2005 #10

    learningphysics

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    Read the other thread Port.
     
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