How does a propeller move an airplane? With this cart, students study the force generated by a motorized fan to learn about thrust, drag, air pressure, and Bernoulli's principle. Attach the sail and students will learn about Newton's law of action-reaction. By varying the angle of the sail in relation to the fan, students can see firsthand what “balanced forces” and “net force” really are. Complete instructions provided. Requires four AA batteries, not included.