Question about speed of a projectile

1. Sep 18, 2010

vande060

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. Sep 19, 2010

vande060

bump

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

and

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