Hacker News Reader

Yes, but dissipating kinetic energy is a solvable problem unlike dissipating momentum.

The initial statement that's being refuted here is that a bulletproof helmet would break your neck and thus cannot work.

This statement is false because (besides such helmets existing on practice) your skull can absorb the momentum without too much damage and helmet can absorb the kinetic energy.

In the movies, the good guy casually fires a shot - one handed. He experiences almost no kickback.

But then the bullet hits the villain’s 300lb henchman, who is lifted off his feet and goes flying.

This is why people think bullets are magical momentum machines when in reality, due to air resistance, the momentum transfered to the target is even lower than at the moment of firing.

It's more the area of the bullet that matters. A small bullet or a thin needle require much less momentum/energy to penetrate a body than a big object.

If you place a bullet between rifle stock and the shoulder, then fire the rifle, it’s going to be mildly unpleasant, but the bullet won’t penetrate the skin, let alone kill the shooter.