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Homework Help: Question about speed of a projectile

  1. Sep 18, 2010 #1
    1. The problem statement, all variables and given/known data

    If a projectile is launched horizontally (in direction of increasing x) with initial speed v0, from a height h above the origin, find its speed s = (v^2x + v^2y)^1/2 as a function of x

    2. Relevant equations

    so far i have the equations for x and y

    y= h - 1/2*g*t^2

    x= v0*t

    3. The attempt at a solution

    i dont understand how to do this problem in the least
  2. jcsd
  3. Sep 19, 2010 #2

    i was thinking,

    x = v0t

    t = x/v0

    y = h - 1/2*g*t^2

    substituting for t

    y(x) = h - 1/2*g*(x^2/v0^2)

    differentiating to get the velocity

    y(x)' = (-g*x)/v0^2


    x' = v0

    then i can put this in the formula

    s = (v^2x + v^2y)^1/2

    s = (v0^2 + [(-g*x)/v0^2]^2)^1/2

    to get speed as a function of x. i dont know if this is right, but its a shot
    Last edited: Sep 19, 2010
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