(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A projectile fired up into the air from the top of a 75m high cliff hits the ground 500m out from the base.

Calculate the initial launch velocity (U), and launch angle (theta) of the projectile.

2. Relevant equations

1) v=u+at

2) v^{2}=u^{2}+2as

3) s=ut+0.5at^{2}

3. The attempt at a solution

Consider up to be positive direction.

Consider vertical component (y component) of motion for entire flight:

a=-9.8 m/s^{2}

s=-75m

u_{y}=Usin(theta)

Sub into Eqn 3:

-75=Usin(theta)t+0.5(-9.8)t^{2}#EQN A

Consider horizontal component (x component) of motion for entire flight:

a=0

s=500m

u_{x}=ucos(theta)

Sub into Eqn 3:

500=ucos(theta)t #EQN B

Now comes the problem... I have created 2 equations (A,B), but with 3 unknowns (u, theta,t). I think I need another equation ???

This is REALLY bugging me, please help.

Thanks very much.

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# Homework Help: Projectile from a cliff - ugh!

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