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Need help finding a derivation of the range formula

  1. Mar 26, 2008 #1
    I need to find a derivation of the range formula for a projectile in the absence of air.

    i know that the range formula is Range=Vhxt
    i know that Vh=vcostheta

    but in having trouble understanding how V=Vo+at can be re-arranged to = 2Vsintheta/g=t where a=g=9.8m/s/s (gravity)

    i know V=Vo+at can be arranged to equal V-Vo/g=t
    but this is where i get stuck, i dont know how to get to V-Vo=2Vsintheta

    i know that vsintheta = vertical velocity

    If anyone can help it would be appreciated heaps
  2. jcsd
  3. Mar 26, 2008 #2
    Because of the symmetry of the parabola, the ball will hit the ground with a vertical velocity of -Vo*sin(theta). So the net change in velocity is 2*Vo*sin(theta) which takes t=2*Vo*sin(theta)/g
    That's a pretty hand-wavy explanation though.
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