Water Power Racers

Challenge: To design a race vehicle that is powered by falling water.

Parameters: The vehicle must be entirely student-constructed from recycled, re-purposed, or found materials, and everything must be recycled, returned, or re-purposed at the end of the project as well. The driving force must be derived from water falling vertically from a 6.2 L plastic container carried by a student following along behind the vehicle. The student must not touch the vehicle at all during the race, unless there is a lane violation.

Scoring: Your racer will compete in a heat of four vehicles and will be considered the winner if it goes 100 m in the least time, or the furthest if nobody makes it to 100 m. If your vehicle has both wheels crossing the lane marker, you must stop, take a penalty of 3 backwards paces, and continue racing until you run out of water or cross the finish line. You will continue to race to determine ranks 1 through 8.

Physics: Falling water converts gravitational potential energy into kinetic energy. It can do work to accelerate your car and to fight friction forces. Your car must harness this energy efficiently so that it can win the race. You will want to minimize the rolling friction of your car so that it won’t require much water to maintain its motion down the track.

Extensions: Early hydroelectric turbines may provide inspiration for your project since that is almost exactly what you are trying to do with your car. Gear or pulley ratios can be used to increase the speed of rotation of your drive axle, and wheel size can be used as well to increase cruising speed of your car.

Help/Hints: Keeping in your lane is very important. It is possible to use the falling water to “steer” your car, not just move it forward. If your car has a reservoir, you can have more control of the water stream, but you will lose energy, and add mass to your vehicle.

Quiz Topics: Kinematics, Newton’s Laws, Forces, Free-Body Diagrams, Momentum, Impulse, Energy, Work, Power, Efficiency, Mechanical Advantage

Timeline: Day 1: Planning

Day 2: Building

Day 3: Building

Day 4: Building

Day 5: Practice

Day 6: Competition