A successful science fair project inspires creativity, provokes students to question their assumptions, and generally involves something defying gravity. You can construct a paper plate hovercraft from a few simple materials, and it serves to demonstrate several important laws of physics. The project offers plenty of opportunities for students to take measurements, record data, and engineer new modifications to improve the hovercraft's performance.
Materials, Construction and Field Testing
Collect a few materials including a disposable paper plate, a balloon, a pair of scissors and a bottle of glue. A disposable pie plate is ideal for the experiment because of the raised edge and the durability of the material. Glue a small square of cardboard to the bottom of the plate. Cut this piece from a separate paper plate and place it in the center of the hovercraft. Using your scissors, create a small hole through the center of the plate and the cardboard square. Pull the balloon opening through the bottom surface of the plate's hole. If the hole is not big enough, try enlarging it just enough to fit the balloon. Do not pull the majority of the balloon through the hole. You may need to adjust the positioning of the balloon as you proceed to blow it up. Inflate the balloon and close the opening to prevent air from escaping. Using a flat, large table, place the plate upside down so the opening of the balloon is directed toward the ground. When you release the balloon, the air will immediately flow out and downward, forcing the plate to hover across the surface of the table.
The Science of Hovercrafts
Newton's third law of motion states that for every action there is an equal and opposite reaction. In the case of the paper plate hovercraft, the initial action is the flow of air, which the balloon projects downward toward the table. As the balloon squeezes the air out, the pressure under the plate increases. The opposite reaction in this case is the flight of the hovercraft off the surface of the table. This reaction is only possible because the hovercraft has much less inertia than the table, and so the hovercraft reacts to the movement of air out of the balloon by hovering upward against the force of gravity.
Once you have a working hovercraft, try experimenting with the model by adjusting some important variables. For example, the size of the hole will affect the rate of airflow out of the balloon. Try enlarging the hole in a second hovercraft and compare how well the two models fly. Another interesting modification involves poking small holes in the edge of the paper plate. Rather than the air escaping from under the plate in all directions equally, this will concentrate a stream of air in a single direction. Again referring to Newton's third law, the action of air escaping the plate's side hole will propel the craft to move in the opposite direction, rather than it simply hovering in place.
Measurements and Data Collection
You can quantitatively measure the lift power of your hovercraft by placing small weights on the top surface of the plate. Start this experiment by collecting some uniform weights; coins would work well for this. Begin adding weights, balancing the distribution of mass across the surface, until the craft no longer rises off the table. Note down the weight as your first measurement, and compare it to the lift power of the other hovercraft models. If you have tried placing holes in the side to create a propulsion air stream, try measuring the distance your hovercraft can travel across the room and compare your results with the other students.
There is nothing more satisfying than students coming up with their own, unique idea that works. Give the students some basic materials, such as construction paper, tape, popsicle sticks, whatever you think might be useful in the modification of paper plate hovercrafts. For example, taking inspiration from nature, students might try to attach a paper fin, or wings, to give the craft some stability during flight.