PURPOSE: To demonstrate the third law of motion.
DESCRIPTION: The carts, initially at rest, are placed at the center of a level track as photographed. The cannon fires its projectile into the receptacle on the other cart when a string is burned, releasing a spring. The mass of the projectile plus the mass of the receptacle cart equals the mass of the cannon cart, so if the carts are started in the middle of the track they will move away with equal but opposite velocities and reach their respective ends simultaneously.
REFERENCES: (PIRA 1H10.30)
EQUIPMENT: Ballistic carts with bullet, string loops and matches on track.
SETUP TIME: 5 min.
Go back to Lecture-Demonstration Home Page.