PURPOSE: To show that the center of mass may remain at rest during motion within the system.
DESCRIPTION: The board is balanced on its fulcrum with the carts touching at the center of the board. Releasing the spring causes the carts to push against each other and separate, but the board remains balanced.
SUGGESTIONS: The experiment can be made more complex by putting a short wooden 2"x4" into one cart, so that the masses of the carts are unequal.
EQUIPMENT: Two PSSC carts, balance board with fulcrum, 2"x4" weight, and stick to release cart spring.
SETUP TIME: None
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