• A boxer delivers a hard blow to the chin of his opponent. The inertia of the boxers hand (with glove) and forearm is 3.0 kg, and the inertia of the opponents head is 6.5 kg. You learned in neurobiology class about 10 J of extra internal energy will render an opponent wobbly-kneed, and you guess that about half of the converted energy will end up in the opponents head. Assuming a coefficient of restitution e = 0.20, with what speed does the boxers fist have to contact the opponents head in order to deliver the punch?