system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - If gunpowder accelerated bullets can barely travel a few feet underwater and aren’t even really lethal, how the hell does a spear accelerated by goddamn plastic bands kill fish from quite a distance?
gpt
It is all about kinetic energy. The kinetic energy depends on the mass and velocity of the projectile. To get enough kinetic energy to kill something you can either use a low mass projectile that you accelerate to very high speeds (such as a bullet going supersonic) or you can have a large projectile going at low speed (such as a spear or arrow). In air it is obviously much better to have something going high speed because it is much easier to hit things with it. However in water there is so much resistance that it is almost impossible for anything to go at speed. So for hunting in water you are much better off with a heavy projectile because then you do not need much speed to get enough kinetic energy to kill the fish.