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Help for physics static and kinetic friction

  1. Jul 9, 2005 #1
    help for physics static and kinetic friction.
    Question:
    A 70 Newtons Penguin is on a 50 N. sled. the static friction between the penguin and sled is 0.671 and the kinetic friction between the sled and the SNOW is 0.119. FInd the maximum horizontal force that can be applied without the penguin sliding off the sled?
    plz post the answer A.S.A.p
     
  2. jcsd
  3. Jul 9, 2005 #2

    Doc Al

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    Staff: Mentor

    Please post your work to get help.

    Hint: What is the maximum value of the static friction that the sled can exert on the penguin? What acceleration is associated with that force? Apply Newton's 2nd law to find the applied force on the sled.
     
  4. Jul 9, 2005 #3
    this is what i did.
    the friction force between sled and snow is= FN X u=(70.1+50)*0.119=14.2919 N.
    the friction force between the penguin and sled = (70.1)*0.671=47.0371, therefore, the max horizontal force that can be applied to the sled without causing the penguin to slide off the sled=14.2919+47.0371=61.329 N. But this is wrong, where m i wrong plz tell me.
     
  5. Jul 9, 2005 #4

    Pengwuino

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    Gold Member

    Did someone say penguin :D
     
  6. Jul 9, 2005 #5

    Doc Al

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    Staff: Mentor

    OK. (But the penguin weighs 70N, not 70.1N.)
    OK. (Same comment.)
    Nope. First find the maximum acceleration of the penguin. (What force acts on the penguin?) Then figure out what force must be applied to the sled so that the sled+penguin has that acceleration. (Don't forget to consider the friction force between sled and snow that must be overcome.)
     
  7. Jul 10, 2005 #6
    THANKS a lot DOC AL, i LUV U lol :P
     
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