In this activity (on page 1 of the PDF), learners will investigate the transfer of energy using sports equipment. Learners first measure how high different kinds of balls bounce compared to their release point and then repeat the testing but release two balls at once, one atop the other. Learners will observe some very surprising and entertaining results. While one ball will go sky high, there is also a measurable difference in the bounce of the bottom ball. Use this activity to explore the relationships between mass and momentum. Relates to the linked video, DragonflyTV: Soccer Ball Kick.