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Tods Workshop on youtube did a video showing that real arrows would not knock someone off their feet.

Imagine a knight in armor is charging on foot at an archer. He wears a breastplate sufficient to prevent penetration. The arrow strikes dead center in the breastplate.

What kind of arrow would it take to knock the knight off his feet?

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  • $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Commented Dec 6, 2022 at 19:08
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    $\begingroup$ A number of shows over the years have investigated the idea of Hollywood-esque blow-the-villian-off-their-feet conditions. The problem you run into is that pretty much anything with the force to penetrate the body will leave the body standing. Only things that don't penetrate the body have the capacity to knock someone off their feet - and then only if the mass/force of the object is greater than the mass/force of the knight. $\endgroup$
    – JBH
    Commented Dec 6, 2022 at 19:14
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    $\begingroup$ In general, any arrow that could knock a charging knight off of his feet would also knock the archer that shot it off of his feet. This is the standard conundrum seen when discussing knockback from shotgun blasts. $\endgroup$
    – Robert Rapplean
    Commented Dec 6, 2022 at 19:16
  • $\begingroup$ @RobertRapplean Please don't answer in comments. $\endgroup$
    – Zeiss Ikon
    Commented Dec 6, 2022 at 19:18
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    $\begingroup$ @ZeissIkon, Really? I write something as an answer and you guys jump my case for writing a non answer, and I write a non-answer as a comment, and you jump my case for that? Is this a contest or something? $\endgroup$
    – Robert Rapplean
    Commented Dec 7, 2022 at 5:42

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Arrows, like bullets, simply don't carry enough momentum to knock a steady-standing human off balance.

To do this, one would need to apply momentum roughly equivalent to accelerating the human target to nearly a meter per second (assuming the target's feet aren't restrained, so they can take a partial step to maintain balance). For an arrow impacting at 80 m/s (a reasonable velocity for an arrow fired from a war bow), the arrow would then have to mass about 1/80 what the target person does -- the latter figure also, of course, including the warrior's armor and equipment.

This comes to an arrow massing a bit more than a kilogram, but still fired at 80 m/s impact velocity; that in turn will require a bow heavier than even an experienced longbow archer could draw.

Now, if you bring in a Roman scorpion (a torsion-powered spear caster capable of hitting a man with a two meter long spear at four hundred meters range) and load it with a blunt head spear, you're in the right range to send enough momentum downrange to knock an armored and ready knight off his feet (but if the bolt isn't blunted, it'll go straight through armor and man instead).

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    $\begingroup$ The most important statement in this answer is, "load it with a blunt head spear." $\endgroup$
    – JBH
    Commented Dec 6, 2022 at 19:17
  • $\begingroup$ Do you know how much such a spear would weigh? $\endgroup$
    – Rebar
    Commented Dec 6, 2022 at 19:20
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    $\begingroup$ @JBH But yes, you need both: enough momentum to impart some minimum velocity to the target warrior, and a way to avoid "wasting" that momentum by punching a hole right through (though punching a hole is historically more effective at discouraging enemies). $\endgroup$
    – Zeiss Ikon
    Commented Dec 6, 2022 at 19:21
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    $\begingroup$ @Rebar I'm confident that a two meter spear that can stand up to being launched from a scorpion will mass more than a kilogram. Just the blunt head would be close to that figure. $\endgroup$
    – Zeiss Ikon
    Commented Dec 6, 2022 at 19:22
  • $\begingroup$ Oh, no argument at all. The reason I remarked about the importance of the blunt weapon is that a fair number of shows (e.g. Mythbusters) and YouTube videos have proven that there's pretty much no momentum you can apply to a sharp something that will knock someone off their feet. Momentum is equally important to the blunt projectile, but not independently important. $\endgroup$
    – JBH
    Commented Dec 6, 2022 at 19:49

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