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Homework Help: Energy problem.

  1. Oct 13, 2008 #1
    1. The problem statement, all variables and given/known data

    A daredevil on a motorcycle leaves the end of a ramp with a speed of 39.5 m/s as in Figure P5.23. If his speed is 38.0 m/s when he reaches the peak of the path, what is the maximum height that he reaches? Ignore friction and air resistance.


    2. Relevant equations

    Eo = mgy

    Ek = 1/2mv^2

    3. The attempt at a solution

    I don't even know where to begin. I need someone to cue me on what equation i should be using because frankly I can't even fathom. I thought perhaps Eo=Ek, but I'm not sure if this is it.
     
  2. jcsd
  3. Oct 13, 2008 #2
    Alright so in the begining the motocycle has Ek only; however, when it reaches the top it gains some Ep therefore some Ek is transformed into Ep due to conservation of energy.

    So

    Ekinitial=Ekfinal+Ep

    Ep = mgy

    Ek = 1/2mv^2

    so

    1/2m(39.5)^2 = 1/2m(38)^2 + m(9.8)y

    Now u can cross out the ms by factoring m from both sides and deviding boths sides by m.
    1/2(39.5)^2 = 1/2(38)^2 + (9.8)y

    y=0.1102556674m
     
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