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Help with newtons laws and friction

  1. Jan 28, 2009 #1
    1. The problem statement, all variables and given/known data
    a girl is skiing down a 35 degree inclined hill that is 120 meters long. She starts from rest and the snow has a coefficient of friction of .12.
    A. Draw an FBD
    B what is her acceleration
    c. How much time dows it take her to travel the 120 meters

    2. Relevant equations
    I am unsure on how to set up the question solution. I think it's CAE's that are used as well, but i am completely unsure.

    3. The attempt at a solution
    ΣF= MA
    vi= 0m/s
    ΛD=120 m
    vf = ?
    120cos35= 98.29????
    120sin35= 68.82????

    If anyone could please help i would really appreciate it. If i can figure out how to set this problem up and solve it, i will be able to figure the other problems out. Thank you so much!!
    I don't think there's enough to solve it using cae's can i use the sin and cosine functions with the 35 degrees??
  2. jcsd
  3. Jan 28, 2009 #2
    You have to take her direction of motion into consideration. If you've drawn a FBD you see that there's a difference in the direction of the forces that have an effect on her acceleration. If you can take this into consideration?
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