Home Show Overview Demonstrations Topics Covered Scheduling Info Feedback

The information below is intended to provide a description of the demonstration, an explanation for elementary students, and further explanation for high school students.

Please keep in mind that not all demonstrations are presented at each show.


Figure I. Figure II. Figure III.


Equipment: Custom-made adult-sized tricycle -- A shelf has been attached to the tricycle on the back of the tricycle, in between the two back wheels. A tube has been built onto the shelf. (See Figure I. and Figure II.) In addition, a brake-type handle has been connected to the handlebars and a cable runs back to the shelf. The cable is attached to a caliper connected to the valve handle of a CO2 fire extinguisher.

5 pound cylinder filled with CO2 at a pressure of 900 pounds per square inch. At this pressure, most of the CO2 has been condensed to liquid.

Bicycle helmet

Step 1: The demonstrator puts on the bicycle helmet and mounts the tricycle. Once aboard, he squeezes the brake-type handle on the handlebars of the tricycle. A blast of gas is sprayed out behind the tricycle and the tricycle moves forward. The demonstrator steers normally and adjusts his speed by using the tricycle brakes and the brake-type handle. (See Figure III.)


Basic Ideas: A gas exerts pressure on all sides of the container which holds the gas. The amount of pressure is related to the energy of the gas and the amount of gas. The higher the energy, the more pressure is exerted, and the more gas is contained, the more pressure is exerted.

Step 1: The CO2 inside the cylinder is being held under a very large amount of pressure. When the demonstrator squeezes the brake-type handle, some of the CO2 inside of the cylinder is released into the air. The pressure inside the container is so great that there is enough force to propel the tricycle forward. Once the tricycle is moving, the demonstrator merely controls the tricycle as he normally would (steering and braking normally). A word of caution must be issued as the gas can often spray out a good ways behind the tricycle.

More Specifically

Related Topics

The following physics topics are discussed during this demonstration:

Sponsored by the Physics Department and the Center for Science, Mathematics, and Engineering Education -- University of Virginia