# Need help finding an angle

1. Oct 17, 2006

### insanitytest

I built a catapult for my physics class and we are required to find the angle and velocity of the catapult (projectile motion). I'm not entirely sure how to do this, can anyone explain please?

2. Oct 18, 2006

### student85

There are several ways to do this. One is measuring the horizontal distance the proyectile reaches when you launch your catapult on a horizontal surface. Then you can use proyectile equations...however you will need to know the initial velocity.
It really depends on your catapult. You could paste a protractor to your catapult and see the angle it reaches at the moment it releases the proyectiles, or if you want to do it more accurately, you could record it, so that later, using slowmotion you can see exactly the angle, using the protractor as reference. Other ways include measuring the time of flight and the horizontal distance to find horizontal velocity.
Lol, lets see what other forumers have to say.

Last edited: Oct 18, 2006
3. Oct 18, 2006

### Danger

What the hell happened to your 'j' key?

4. Oct 18, 2006

### bkvitha

lol.... "j" key----was it his mistake of using the word proyectiles?!

it is projectiles, isn't it?

5. Oct 18, 2006

### Danger

Jes.

6. Oct 18, 2006

### student85

lol. english is not my first language. in spanish it´s proyectiles. haha excuse me.

7. Oct 18, 2006

### way2lazy2care

find how high and how far it goes, if it's a moderately sized catapult air resistance shouldn't be a problem... take the height to figure out it's original speed in ^ that direction, then take the distance along with it's flight time to find it's speed(which should remain close to constant) in > that direction... then take these to speeds, and use trig to figure out the velocity and the angle of it...

8. Oct 19, 2006

### Danger

No problem, pal. I rather figured that such was the case. My post certainly wasn't meant to ridicule you; I just saw the opportunity for a joke and went for it. (And although I can't speak it, I'm actually part Spanish myself.)

9. Oct 19, 2006

### billiards

I would try to measure it by setting up a video recorder perfectly side on from your catapult and taking repeat recordings. Try to set up a screen behind your catapult with square gridlines (number the rows and columns for reference) and get everything nice and horizontal, then if you can get a digital image on your computer you can trace the path quite accurately. Ideally you want to be a fair distance to minimise error, if you've got a good zoom use it.