We’ve all seen the moment in a movie when our hero blasts away or is blasted away by
their nemesis.
The lump of lead explodes out of the barrel, propels through the air and smashes into their
body part of choice, this knocks the target clean off their feet and sometimes, depending
on the firepower used, into the air, where gravity quickly takes over bringing them crashing
down to earth in dramatic style.
But have you ever wondered, how realistic this is?
Can the momentum of a speeding bullet be enough to lift a bad guy into the air?
I’m Stu, this is Debunked, and we’re here to sort the truths from the myths, and the
facts from the misconceptions.
Like, subscribe and leave us a comment now about whether you thought a bullet could actually
do this or not.
Now, if you’ve grown up watching movies depicting villains and their dutiful henchmen
being launched backward into the air upon being shot, you might never have thought that
the reality could be any different.
Of course, guns are very dangerous weapons, especially some of the more powerful ones,
so it’s not entirely outside the realms of possibility that a human being could be
significantly knocked back by a sufficiently burly bullet, right?
As usual, it is the trifling matter of physics that reveals the problems with this classic
movie trope.
First of all, bullets aren’t designed to knock you backward;
they are designed to break through your skin, cause as much internal damage as possible
and, y’know, kill you.
Ranged weapons utilise high kinetic energy focused on a small area at the tip of the
bullet,
enabling penetration of the skin and access to your fragile, gooey insides.
Indeed, bullets are so deadly specifically because they are small lumps of relatively
hard metal with relatively little mass, making them fantastic at flying through the air at
high speeds before ripping through much softer biological matter.
However, as bullets are ultimately still just small lumps of metal, usually weighing only
a few grams, they lack the necessary momentum required to knock over an entire person, as
the average human being usually weighs significantly more than just a few grams.
Obvious practical concerns aside, if bullets were meant to dramatically throw a person
backwards upon impact, they’d have to be a lot bigger, heavier and flatter in order
to exert their force over a large area of your body without just tearing into your flesh
like a regular bullet.
And not for nothing, while the effects of such a projectile on a person would undoubtedly
be unpleasant, they would likely be far less fatal.
Perhaps unsurprisingly, there actually has been some academic interest in this popular
movie cliché, and for quite a long time too.
In 1996, an article published in the International Journal of Legal Medicine assessed the physics
of the displacement of the human body upon being shot full of proverbial lead.
It states the following:
“The maximum momentum transferred from different small arms projectiles including large calibre
rifles and a 12-gauge shotgun
only results in a backwards motion of an 80 kg target body of 0.01-0.18 m/s,
which is negligible compared to the velocity of a pedestrian (1-2 m/s).”
“Furthermore, counterbalance is constantly maintained by neurophysiological reflexes.”
“So the effect of the momentum transferred from the missile is virtually zero and there
is no backwards motion of the person shot.”
In layman’s terms, this essentially means that most gunshots from regular firearms only
impart a knockback of a few centimetres per second;
even being shot by a 12 gauge shotgun will only push you - or part of you - back a maximum
of 18 centimetres per second.
This movement will also diminish to nothing almost immediately after the initial impact,
in part because,
assuming you weren’t shot in the head,
your body will reflexively respond to the hit and compensate accordingly.
Ultimately, the amount of backward motion caused by even the most powerful firearms
ranges from minimal to pretty much negligible.
And the physics issues don’t end there.
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Right back to the physics issues.
You also may have noticed that while this classic trope frequently involves the victim
being blown backwards into the air, stopping only upon impact with the wall behind them,
the person doing the shooting never seems to be affected beyond the standard kickback
you would get from firing a regular gun.
This violates one of the most fundamental concepts in physics, namely Isaac Newton’s
Third Law of Motion, which famously asserts that for every action, there is an equal and
opposite reaction.
This isn’t usually a huge problem when firing a regular gun, as the gun itself has considerably
more mass than the bullet it is propelling and is also equipped with a nifty little handle,
which makes absorbing recoil fairly easy.
However, if there were a firearm capable of blowing enemies into the air, Newton’s pesky
Third Law dictates that it would exert the exact same amount of force on the person firing
it, meaning that even if you could create such a weapon, the user would necessarily
be blown off their feet as well… not ideal.
So, it’s fair to say that bad guys flying all over the place after being shot by a regular
firearm is a slight exaggeration.
But perhaps we’re being a little too hasty in dismissing this trope entirely; are there
any circumstances under which being shot can significantly propel a person backwards?
For instance, what if you get shot with a relatively powerful firearm whilst wearing
a bulletproof vest?
If you’re wearing something that prevents bullets from penetrating your body, and all
that kinetic energy has to go somewhere, surely the impact you’ll experience will be much
greater than if the bullet went straight through you?
Well, yes, that is true.
But it still wouldn’t be anywhere near enough to create the comically large knockbacks that
you see in certain films and television programs.
Most bullets are still far too small to forcibly hurl a person into the air even if they are
prevented from puncturing you.
Furthermore, even though bulletproof vests are very good at dissipating energy from gunfire,
they are not 100% effective, and it is possible that bullets fired from sufficiently powerful
firearms could make it through.
Guns that actually are powerful enough to knock a person backwards or up into the air
are not handheld;
they are artillery weapons that are either attached to sturdy support frames that stand
directly on the ground,
or are mounted onto heavy, fortified vehicles like tanks and warships.
And frankly, the kinds of projectiles that these guns fire are often the sort that don’t
merely blow people into the air; they blow them to smithereens.
In reality, when people get shot, they don’t get thrown backwards -
- they collapse and fall.
Sure, if a person is shot when they’re off balance or leaning backward, they might fall
pretty far, especially if they manage to take one or two steps before they actually go to
ground.
And of course, there are some particularly powerful firearms that exert considerably
more force on a target and hit far harder than your average handgun.
But as Doctors Kneubuehl and Karger put it, this is a myth that is easy to disprove but
hard to destroy,
because not only is it a staple of nearly every action movie, but in the real world
so many medical professionals don’t understand the physics of what happens to the human body
during gunshot wounds.
“So-called experts again and again tell Judges that a bullet will knock down a man
or throw him backwards.
If this statement is not refuted in the courtroom, the person accused of shooting someone may
suffer a miscarriage of justice.”
So, as for literally being blown off your feet, much less thrown across a room or through
a glass window in dazzling slow motion…
I’m afraid, my friends, that those are the lies of sweet lady Hollywood.
Not that we’re complaining.
This classic movie cliché may be entirely unrealistic, but that doesn’t mean it isn’t
very, very cool.
Pass the popcorn.
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