Working Wood Catapult Kit

This catapult is simple in concept and easy to assemble. It takes some care to get all the parts aligned and wind up the string-based torsional spring but, once assembled, it can shoot small rocks (1-5 grams) 10-20 meters. Be careful in winding up the torsional spring as overwinding can result in breaking the top crossbar that absorbs excess energy from the catapult 'spoon.' I have had to reinforce/rebuild several crossbars using pine shims but the extra throwing power is worth the extra work - plus it's a good demonstration of the strength of materials and how they can be augmented with a stack of simple components. I have used this unit to demonstrate the acceleration of bodies for a standstill and explain how semi-circular motion transfers momentum in a tangential relationship to the thrower. It is also useful in showing the relationship between the force of the thrower and the mass of the thrown object are related - a specific mass results in a maximum throw distance. This is related to the torsional spring tension and can be easily demonstrated by repeated trials. Setting up multiple catapults with class groups can be entertaining and edifying at the same time.