Monday, June 6, 2016

A Quick Note on Bullets

I have two guns, one for each of you.
You know that moment in the movies where the big bad is coming at one of the heroes, and swinging some blunt force object, like a sword or tank, and there’s just no way to avoid the hit which is certainly going to be the end of that character . . . but then, but then . . . another hero, unseen by the camera or the big bad shoots—BAM! BAM! BAM!—right in the chest.  The big bad goes flying backward, a distance that puts most professional quarterbacks to shame, and thus the day is saved?

Yeah, sorry, but that’s not how bullets work.

There’s even an equation for it, and unlike most physics, this one is very straight forward:

p = m ∙ v

Translated into Rob dummy talk (I had to look it up):

momentum = mass times velocity

Simply put, even though a bullet has a high velocity, it doesn’t have a lot of mass, and thus it doesn’t have a lot of momentum.  Even large caliber bullets aren’t going to change the
That's not how bullets work!
outcome much because, by design, they lack mass.  A bullet’s whole point is to be relatively small object so that it can strike and penetrate the “big bad’s” body at a distance. By comparison, a boxer can knock someone back with a punch because her fist and her body behind it, have nearly equal mass to the big bag being punched in his smug, evil face.  The boxer is strikes with a larger mass and a decent velocity against a larger area, thus creating the momentum needed to knock someone off their feet.

You wouldn't expect to see a boxer punch through someone unless they're trained to pull the big bad’s still-beating heart of their chest so they can see how black it is before they die. Whereas a bullet is designed to do exactly that.  Showing the big bad how black his heart is becomes quickly moot.

I believe the MythBusters did an episode on this, but I was unable (after 2 minutes and 38 seconds effort) to locate it.  However, I easily found this video, which first falls under the "don't try this at home" category, and second falls under the “maybe dying for science is a bad idea”.  Still, it serves our purposes nicely:

So, as you’re writing that urban fantasy, and place your character in danger from blunt force trauma, remember that the big bad isn’t going to be thrown backward by a bullet.  If he’s standing still, he’ll drop to the ground.  If he’s attacking and in motion, then he, and whatever weapon he’s carrying, will remain in motion, because there isn’t enough momentum in the bullet to stop it.  This is even better, because it creates a more realistic scene, and can provide for a much narrower escape!

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