During medieval times, soldiers used catapults, also known as trebuchets, to hurl stones or other heavy objects at fortress walls. A modern adaptation of the catapult is capable of launching aeroplanes from aircraft carriers. As a science fair project, the catapult helps students explore and demonstrate concepts and physical properties such as gravity, conversion of potential energy to kinetic energy and mechanical advantage.
Students may purchase a catapult kit that is capable of firing a marble up to 30 feet from the Catapult Kits website (at catapultkits.com). This kit allows students to experiment with a variety of firing methods and to design experiments to test which launching methods work best. Another catapult kit, available from Abong.com (abong.com), stands 10 inches high and accommodates experiments at every educational level, from elementary school through college. This model may be configured to function as a wheeled, sling trebuchet or a bucking spoon-arm onager.
Catapult Building Plans
Redstone Projects carries a number of building manuals for catapults and trebuchets (at redstoneprojects.com). Students may choose from models such as the torsion catapult, da Vinci trebuchet, a golf ball trebuchet made with PVC and a 6-foot-tall model that is capable of hurling tennis balls, racket balls and water balloons.
The website of the University of Illinois' BOAST program (which stands for Bouchet Outreach and Achievement in Science and Technology) contains an easy and inexpensive catapult science project (at life.illinois.edu). This project uses a mousetrap, erasers, marshmallows, a rubber band, erasers, Popsicle sticks, a spoon and duct tape to explore the mechanics of simple levers, as well as related concepts.
Ping Pong Catapult
The Science Buddies website provides instructions for a tabletop catapult powered by rubber bands (at sciencebuddies.org). In this science fair project, students experiment with independent variables -- ball type, angle of launch, pullback angle and number of rubber bands -- to discover which launch conditions lead to the greatest target-hitting accuracy.
Washington State Experiment
In March, 2006, then 13-year-old student Avery M. entered the Washington State Science and Engineering Fair with a catapult experiment designed to test the effect of a projectile's weight on the distance the projectile can travel when hurled by a simple tabletop catapult. On the Washington K12 website (selah.k12.wa.us), Avery shares the details of his experiment, including materials, hypothesis, procedure and results. Avery also provides historical and scientific background information.
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