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Basic Physics Problem. Please Help

  1. Jul 3, 2009 #1
    A 71.8-kg skier coasts up a snow-covered hill that makes an angle of 25.1 ° with the horizontal. The initial speed of the skier is 8.84 m/s. After coasting a distance of 2.10 m up the slope, the speed of the skier is 3.41 m/s. (a) Find the work done by the kinetic frictional force that acts on the skis. (b) What is the magnitude of the kinetic frictional force?

    Part a= -1761 J

    I Just cant figure out how to find part b
     
  2. jcsd
  3. Jul 3, 2009 #2
    What is the definition of work done?
     
  4. Jul 3, 2009 #3
    Work done is equal to KE+PE so kinetic energy final + mgh- kinetic energy intial+ mgh where kinetic energy is 1/2mvsquared
     
  5. Jul 3, 2009 #4
    There is another definition of work done which says
    [tex]W=r \cdot F[/tex]

    Try it now.
     
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