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Find the initial velocity of a projectile

  1. Sep 25, 2013 #1
    1. The problem statement, all variables and given/known data
    So it's based off of a track&field long jumper. Calculate the initial speed, v0, of a long-jumper where d=7.87 m. Assume a take-off angle of 21.4°, an initial height of the centre-of-mass of 0.920 m, and a final height of 0.460 m.

    So I use the range equation for projectile motion and rearrange it for velocity but it doesn't seem to work...

    can someone correct me?

    2. Relevant equations
    x = v^2/gsin2(theta) where x is the range. i rearranged for velocity.

    3. The attempt at a solution
    x = v^2/gsin2(theta)

    v = sqrt(xgsin2(theta)
    = sqrt(7.87m*9.8*sin(2*21.4)
    = 7.24 m/s
  2. jcsd
  3. Sep 25, 2013 #2
    Your equation works when initial and final height is the same. Here it isn't
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