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Force and work

  1. Oct 4, 2007 #1
    A child pulls a 15kg sled containing a 5kg dog along a straight path on a horizontal surface. He exerts a force of a 55N on the sled at an angle of 20 degree above the horizontal. The coefficient of friction between the sled and the surface is 0.22 .
    Find:a) normal force of the surface on the system , b) the acceleration of system, c) the work done by the child as the system move 7m.
    This is how i approach them

    a)normal force = Force of the child exert - Force of friction
    55cos20 - .22( (15+5)9.8 ) = 8.563 N

    b)normal force= ma
    8.563N = ( 15+5 )a
    a=.428m/s^2

    c)W=Fd W=8.563(7)= 59.94J

    give me suggest if im make a mistake
     
    Last edited: Oct 4, 2007
  2. jcsd
  3. Oct 4, 2007 #2
    What do you understand "normal" to mean when talking about surfaces?
     
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