Rubber band-powered cars can teach kids about physics and engineering principles such as kinetic and potential energy, friction and inertia. Kids can build rubber band-powered cars with materials found around the house or classroom and it will trigger the child's imagination and her problem-solving skills. Encourage kids to experiment with different designs and materials as they build their cars. They can also experiment with different "motors" using both long, skinny rubber bands and short, fat ones. Experimentation can prepare students for rubber band-powered car competitions where they can show off their knowledge and skills.
The PBS Design Squad provides online plans for building a two-wheeled dragster out of two CDs, a wooden skewer, some poster tack, a piece of corrugated cardboard, tape and, of course, a rubber band. The construction of this car is simple and it performs well. It makes a great starting point for kids to begin modifications of and improvements on a simple design.
Give kids a cheap rubber band-powered model aeroplane kit available at any craft or hobby store and ask them to build a car powered by its rubber band and propeller. They can build the frame of the car out of cardboard, balsa or other materials. With its power coming from the thrust of air produced by the propeller, this project is useful for teaching the principles of action and reaction.
Rubber band-powered cars can be constructed from LEGO bricks, gears and wheels. Students can even experiment with different size gears to see how gearing changes affect their car's speed and distance. Designs for LEGO cars are available on the Internet. Encourage students to improve on existing designs or to design their own unique cars.
A rubber band-powered car does not need to carry its power source with it. Challenge kids to create a car and a launcher that will catapult the car forward. The design challenge will include figuring out how to create a launcher that does not interfere with the car's motion but also delivers maximum power to the car. Catapult cars will likely go further and faster than other rubber band-powered cars. You will need a large gym or an empty car park in which to test them.
Challenge students to design a rubber band-powered car that can operate on land or in water. You can then organise a two-stage race in which cars win points for speed or distance over each surface.