# Which Catapult would work best?

1. Sep 14, 2006

### Iceman2032

I'm not sure if I posted this in the right thread, if not feel free to move it.

I have been assigned to build a catapult as my physics project. I have researched a bit and saw some examples. The main purpose of the catapult will be accuracy.

First of all, I wanted to ask you experts which of the following catapult systems will be more accurate?!

1. We use a weight as the source of energy. Think of it as a pendulum. The weight at the bottom of the beam moves back, the beam will go forward and the projectile at the top will be launched.

2. We use a spring rather than the weight. The spring pulls the beam to itself, then the beam will come to a sudden stop and cause the projectile to be launched.

The only thing that really matters is the accuracy here. I need to be able to hit a target within 8 meters of the catapult.

Another question is what effect will it have to extend the beam? Will it cause more velocity?! I was playign with this catapult idea and this idea popped that it would be cool to have the arm actually have a variable length. Will that help at all? Or is it just a waste of brain cells (I know I need to do lots of calculations)?

Also if I were to use the spring as teh source of energy, how can I calculate the force of it and all?! I mean with teh weight it's just the pendulum...easy. Butthe calculations with the spring are kind of foggy in my head. Can someone shine a light on that too?

Any help is appericiated