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Homework Help: Bike on a hill

  1. Feb 21, 2007 #1
    1. The problem statement, all variables and given/known data
    I wasn't sure if i was doing this problem correctly, if anyone could double check for me, that would be great!
    You ride your bicycle down a hill. Your total mass is 40 kg. At the top of the hill, your
    speed is 5 m/s. The hill is 20 m high and 200 m long. If the force of friction is 20 N, what is
    your speed at the bottom of the hill?






    2. Relevant equations



    3. The attempt at a solution
    Top =
    KE = 1/2 m v ^2
    KE = 1/2 (40) (5)^2 = 500

    PE = mgh
    (40) (9.8) (20) = 7840

    W = Fd
    (20)(200)= 4000

    7840 - 4000
    =3840

    3840 + 500 = 4340 = 1/2 (40) v ^2
    divide both sides by 20
    take the square root, and got 14.7 as my answer...
     
  2. jcsd
  3. Feb 21, 2007 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Looks ok to me. Though I'd be more careful about putting units on things.
     
    Last edited: Feb 21, 2007
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