Purpose: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 one another at the center of the board. Releasing the spring causes the carts to push against each other and separate, but the board remains balanced.
Questions: What would happen if the two carts had different masses? Would the board become lopsided?
The experiment can be made more complex by putting an extra weight into one cart, so that the masses of the carts are unequal.