So a friend and I started a debate over dinner, and no-one around here really wants to side with either of us, since neither of us has any concrete facts on the issue. The issue is this: Which would have a greater chance of causing a fatal impact on someone, a wooden bat or an aluminum bat. Grim topic, I know. At any rate, my argument is thus: since the aluminum bat is made of a thin metal wall and a hollow center, it would tend to flex during impact, increasing impact time. In the end, the energy imparted is greater (like a trampoline, but those aren't painful to jump on!), but since it is spread out over a comparatively longer time, it would cause less injury. Conversely, the wooden bat is more rigid(being solid) and connects with the target and rebounds quickly away, with a near zero length of impact. I am under the impression that injury is caused by sudden changes in velocity (not the fall that kills you, but the sudden stop!), and given a near zero time for a subject's velocity to change, it would almost certainly break in some painful way. That said, either construction bat would be lethal at any reasonable velocity, so we're talking borderline cases. Given a two subjects (lets say they're identical twins, fed exactly the same so their juicy skulls have grown in precisely the same manner) and two bats, one typical aluminum construction, and one typical wood construction, with the same mass, you hit each person in the head with the bats starting at 1mph and working your way up in 1mph increments until one of them suffers a fatal injury, which bat would be the culprit? None of this was outlined in our debate, however, I just came up with this for the sake of consistency. PS. Hello physics forum, hopefully this site can solve many debates!