Which collision imparts more momentum—an object that hits a block of wood and sticks to it, or an object that bounces straight off? The answer will knock over one of the blocks, not to mention your students! This simple but effective demonstration uses two different types of rubber balls that swing into wooden blocks to distinguish between elastic and inelastic collisions. One ball is very resilient, or bouncy, and will rebound to its initial height or position when striking a surface. The other ball hardly bounces at all as it absorbs all of the energy from a collision. What happens afterward can be described mathematically using equations to compare conservation of momentum in the two cases. Your students are much more likely to understand and remember the results, however, when they see them in action! Includes student worksheet and comprehensive Teacher Notes with lab hints and teaching tips as well as answers to discussion questions.