Question

Which is the best example of the law of conservation of energy?

A basketball stops bouncing because its energy disappears.
A rolling skateboard slows down because some of its kinetic energy changes to heat.
A falling book hits the ground and all of its energy is destroyed.
A toy car gains speed as it moves down a ramp because the ramp creates energy

Answer 1

"A rolling skateboard slows down because some of its kinetic energy changes to heat."

This correctly describes energy being transformed (from kinetic to thermal and other forms) rather than created or destroyed, which matches the law of conservation of energy.