How can I make a simple catapult??? read below?

Question

with a rubber band, some type of box for a base, a container cap to hold a marshmallow, popsicle stick etc. (anything at home) i want it to look like this animation: http://www.howtobuildcatapults.com/catapultmangonelanimation.html

Answer 1

In your example, the arm of the catapult
was driven by a twisted rubber band.
You might get more power by just
stretching the band back from a frame.