PURPOSE: To demonstrate the third law of motion.

DESCRIPTION: Two gliders (either M and 2M or M and M) are tied together with a string loop against the force of a compressed spring. Burning the string releases the gliders with no external force. The photogate timer measures the time it takes for each glider tab to move through its respective gate. A reset switch on a cable clears the timer between measurements without the instructor getting in the line of sight.

SUGGESTIONS:

REFERENCES: (PIRA 1H10.15 and 1N20.20)

EQUIPMENT: Air track with two mass M and one mass 2M gliders, string loops with burner, photogates and timer.

SETUP TIME: 5 min.