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Homework Help: A skateboarder hits a ramp

  1. Oct 14, 2007 #1
    1. The problem statement, all variables and given/known data

    A skateboarder starts up a 1.0 m high 30 degree ramp at a speed of 7.0 m/s. The skateboard wheels roll without friction. How far from the end of the ramp does the skateboarder touch down?

    3. The attempt at a solution

    ramp length=
    h=1sin30=1/2
    length=2m

    v^2=vi^2+2ad
    v^2=7^2+2(-9.8)(2)
    vf=3.13m/s

    vf=vi+a(Dt)
    0=3.13+-9.8(t)
    delta t=.32s

    Xf=xi+vi(dT)
    x=0+3.13(.32)
    xf=1.0016

    yf=yi+vi(dt)+1/2a*(dt)^2
    yf=1+0(.32)+1/2(-9.8)(.32)^2
    yf=0

    The skateboarder lands 1.0016 meters from the end of the ramp.




    I know I'm missing something somewhere... can someone please help me find it.
     
  2. jcsd
  3. Oct 15, 2007 #2
    Hmm... That wasn't even close... Let me try this again.

    cos30(7)=vx= 6.06 m/s
    sin30(7)=vy= 3.5 m/s

    -1=3.5(t)+.5(-9.8)(t^2)
    0=-4.9t^2+3.5t+1
    t= 0.933 s

    x= (6.06)(.933)+.5(0)(.933)^2
    x= 5.65 m

    How does that look?
     
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