Action-Reaction Forces with Air Table

Concept Overview

As the car moves forward, the glass plate moves backward in accordance with Newton's 3rd Law.

Lecturer Procedure

Steps to Follow

1. Turn on air pump.
2. Put glass plate diagonally in front-left corner of air table (when facing the class).
3. Place car on glass plate and pull back (away from corner of table).
4. Release car.

Expected Result

Glass plate will move backward; car will move forward.

Historical References; Taken from original work of Percy H. Carr, 1970 

“If the earth were light enough, the motor of an automobile would drive the earth backward more than the car forward; and that is what this experiment is designed to emphasize.”

“Note: If all forces and motions are not kept on the longitudinal axis of symmetry of the glass plate through its center of mass, rotation of the plate will result. This rotation will usually be too small to be noticed except by those very near the front. With care it can be avoided.”

Video Demonstration

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