Students will calculate the potential and kinetic energy of a popper toy using simple formulas. Potential energy is found by observing the maximum height. Kinetic energy is found by using a dynamics formula to find the popper's starting velocity. Students will find that the popper reaches a greater height than it should, given the amount of kinetic energy it started with! The discrepancy is resolved by finding the amount of energy stored in the elastic deformation of the popper.