# Help with catapult calculations

1. May 17, 2012

### Cata-tonic

hi so i had to build a catapult and it's very small, but i need to find the total velocity of the ball upon impact and the maximum height reached. You might need to explain a little bit because I tend to not get things when they are vague so please post more than a formula. Please and thank you so much!!

2. May 17, 2012

### haruspex

Sounds like you have the catapult and your problem is what to measure in order to be able to estimate these other values, yes?
Are we talking of something hand-held or field artillery?
What mechanism is in use? Need to know how the applied force varies during launch. Knowing that, if you can then measure the peak force you can estimate the launch speed. Everything else follows from that.

3. May 18, 2012

### the_emi_guy

I'm thinking if he can measure how far downrange the projectile landed, and the angle with which it left the catapult (90 degrees minus release angle of catapult arm) then we can show him how to compute the other stuff.

4. May 18, 2012

### jssamp

That's what I did. Learned tons about ballistics while figuring out formulas to estimate performance. Hardest was the formula to find v_0 from range and launch angle. Cool project, built it mostly out of aluminum, with steel leaf springs to provide the force. Cables from the ends of the spring wrapped around a ratcheting drum. Anyway, if you need some help...