Posted by physics on .
i have to build a catapult that will fire a projectile that will pass a 1m tall wall 1 m away from starting point and land in a target 1 m away from the wall. the catapult cant be more than 23cm high.
I'm having some problems here with this
for simpicity issues
i said launch at .2m off the ground at origin and reach a height of 1.1m at 1m away just incase something screws up.
I need to find the
Vi
Vyi
Vxi
and am having some trouble and don't know what angle is best so that less speed is needed for this to work

physics 
drwls,
You have selected 0.2 m for the initial height and 1.1 m for the maximum height. That allows you to calculate the time the projectile must spend coming down (t2) and going up (t1).
(g/2) t2^2 = 1.1 m
t2 = 0.474 s
(g/2) t1^2 = 0.9 m
t1 = 0.429 s
Initial y component of velocity:
Vyi = g*t1 = 4.204 m/s
Total time of flight = 0.903 s
Vxi*0.903 s = 2.0 m
Vxi = 2.214 m/s
Vi = sqrt(Vxi^2 + Vyi^2) = 4.751 m/s
These two components determine the initial launch angle as
arctan(Vyi/Vxi) = 62.2 degrees