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Find the horizontal force

  1. Nov 23, 2008 #1
    A hors og mass 509 KG Pulls a sleigh of mass 255 KG and both horse and sleigh accelerate 0.5 m/s^2. the coefficient of friction for the sleigh is 0.150 as it moves over the snow. Find the horizontal force that the horse must exert on the sleigh. Remember sleighs have two identical blades on the snow

    Ff= 0.150*9.8*255*2= 749.7N
    Ft-(255*9.8)-(749.7)=509*0.5
    Ft-3248.7=254.5
    Ft=254.5+3248.7
    Ft= 3503.2N
     
  2. jcsd
  3. Nov 24, 2008 #2

    PhanthomJay

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    Re: Help

    Ff = uN, where N=the weight of the sleigh = 255*9.8N. That '2' doesn't belong there; the problem was trying to throw you off. Ff = 375N , and it acts in the negative x direction.
    I assume by Ft you mean the force of the horse on the sleigh. Ft is in the x direction. For starters, that sleigh weight, 255*9.8, which acts in the vertical direction, doesn't belong there. You're looking for net forces in the x direction. Look at the horse and sleigh together. In the x direction, F_net = (m +M)a, where (m +M) is the combined weight of sleigh and horse, and F_net , the forces pulling on the sleigh in the x direction, is (Ft -Ff). So it's Ft -Ff = (m + M)a. Canyou sove for Ft?
     
  4. Nov 24, 2008 #3
    Re: Help

    I think that

    Ft=375 + 382
    Ft=757N
    But do you think the force (757N) can move the sleigh ( 2499N)?
     
  5. Nov 24, 2008 #4

    PhanthomJay

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    What do you think? Ever been to an airport and seen a rinky-dink tow truck pull a 1,000,000N 707 jetliner?
    Why is this so?
     
  6. Nov 24, 2008 #5
    Re: Help

    Ft=375 + 382
    Ft=757N
    i that right
     
  7. Nov 24, 2008 #6

    PhanthomJay

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    looks ok, but you didn't answer my question.
     
  8. Nov 24, 2008 #7
    Re: Help

    Thanks for your help

    I don't know about it but could you tell me
     
  9. Nov 24, 2008 #8

    PhanthomJay

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    Re: Help

    The pulling force need only overcome friction to move it. If there were ideally an theoretically no friction between sleigh and snow, you wouldn't need to pull it with a horse to move it, you could move it with a gentle shove.
     
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