Mythbusters - "Knock My Socks Off"

[Trekker4747]

The episode's title refered to the silly "busting an idiom" myth the "junior mythbusters" did regarding if it's possible to "really" knock someone's socks off.

Jamie and Adam had the greater and more amazing myth.

They dealt with the physics thought experiment that a dropped bullet and a bullet fired from a gun will hit the ground at the same time (since the fired bullet is subjected to gravity as much as the dropped one being that it can't produce lift, or propulsion to stay in the air.)

After up-scaling tests from ball bearings to paint balls, tests with guns, they finally set up a rig to test if a fired bullet and a dropped bullet hit the ground at the same time -setting up cameras at their predicted "landing spot" to see if they strike at the same time.

Spoiler: Their findings

The dropped bullet and the fired bullet hit the gound 39.6 miliseconds apart, or "at the same time." Since 39.6 miliseconds is an irrelevant ammount of time and likely would count for the "margin of error" in their rigs and timing and is far faster than the human eye can see.

 

[Christopher]

Yeah, the bullet thing was interesting, but I found it kind of silly that they devoted so much effort at the end to rigging a system that would let them drop and fire simultaneously just so they could get the "cool shot" of the fired and dropped bullets hitting the same place at the same time. The data would've been just as valid if they'd conducted the tests separately. Still, this is a television show, and I guess it was a pretty effective visual proof of the principle.

There did seem to be a tiny slowdown in the bullet's descent; I'm assuming they did more than one test and only reported the average, since these experiments are always edited way down for television. I'm wondering if there could've been a tiny bit of lift, even just an insignificant amount, on the bullet in flight. I mean, it's spinning for stabilization, right? And it must have some tiny imperfections. So there might be a very faint vortex like around a curve ball. I don't know... hard to test, though.


On the socks, at first I was wondering if maybe having sweaty feet would make the socks more slippery, but then I realized it would probably make them stick more. Still, maybe if the socks in question were old, worn, and loose, they could fly off more easily. I've had old socks that would hardly stay on, that you could essentially fling off just by swinging your foot a few times. So I'm not quite ready to say the myth is busted.

Though it's pretty clear that the expression is an exaggeration, coined for hyperbole and assonance rather than based on direct observation. We've seen that impacts can knock shoes off, but "knock your shoes off" doesn't have that internal rhyme, so it's inevitable that it would've mutated into "knock your socks off."


I had kind of an "aww" moment when Kari pointed to her pregnant belly and referred to the "little Mythbuster" within. Boy, if this show keeps running long enough, that kid could have a pretty interesting childhood...

 

[Roger Wilco]

Yeah, the bullet thing was interesting, but I found it kind of silly that they devoted so much effort at the end to rigging a system that would let them drop and fire simultaneously just so they could get the "cool shot" of the fired and dropped bullets hitting the same place at the same time. The data would've been just as valid if they'd conducted the tests separately. Still, this is a television show, and I guess it was a pretty effective visual proof of the principle.

Yeah, they could have easily measured the time difference between the bullet leaving the gun and the bullet getting dropped from the magnet and subtracted that from the final result.

But I give them props for doing the test honestly instead of just rigging it in such a way that it looks the two bullets "started" simultaneously on camera - which they could have easily done without any of us ever knowing too.

 

[Christopher]

But my point is, they didn't have to conduct the tests simultaneously at all. As far as the science was concerned, they could've done it just like their earlier tests -- first time the dropped bullets, then time the fired bullets, and compare the numbers. Doing them simultaneously was purely for show.

 

[Roger Wilco]

Yes, but usually it's not necessary to blow up stuff for scientific reasons also and they do it anyway because it looks good on tv.

 

[Christopher]

Is it just me, or do most of the myths these days fall into three categories: guns, cars, and explosives? Sometimes I wish the show were on a channel that isn't so "guy"-oriented.

 

[davejames]

I admit I was a bit surprised by the bullet thing (not that I had really given the idea much thought before). Of course I was assuming they'd be firing upwards; I didn't realize how much a difference it would make just firing parallel to the ground.

And as for the socks, I imagine back when the idiom originated they weren't as elastic and form fitting as they are now. And people probably kept them a lot longer too, until they got really worn and loose.

 

[davejames]

Is it just me, or do most of the myths these days fall into three categories: guns, cars, and explosives? Sometimes I wish the show were on a channel that isn't so "guy"-oriented.

I don't mind the gun and car thing (as long as the myths are interesting, I don't really care one way or another), but they definitely need to cut back on the explosions.

If they're using an explosion to TEST something, that's fine, but I hate when they stick some explosives in something at the end of the episode just to see it blow up.

 

[backstept]

Is it just me, or do most of the myths these days fall into three categories: guns, cars, and explosives? Sometimes I wish the show were on a channel that isn't so "guy"-oriented.

I don't mind the gun and car thing (as long as the myths are interesting, I don't really care one way or another), but they definitely need to cut back on the explosions.

If they're using an explosion to TEST something, that's fine, but I hate when they stick some explosives in something at the end of the episode just to see it blow up.

well I love when they stick some explosives in something at the end of the episode just to see it blow up

 

[tharpdevenport]

To be fair, they usually do that if the myth has been busted, or can't get it done. They don't just arbitrarily drop the myth and blow the shit out of something.

 

[Christopher]

I admit I was a bit surprised by the bullet thing (not that I had really given the idea much thought before). Of course I was assuming they'd be firing upwards; I didn't realize how much a difference it would make just firing parallel to the ground.

Either way, the physics will be the same. No matter what path a bullet follows, gravity is pulling on it at the same rate. If you fire a bullet at an upward angle that causes it to crest, say, twenty feet above the barrel height before it falls back downward, the vertical component of its motion would be identical to that of a bullet tossed directly upward twenty feet, and they would both take the same length of time to hit the ground. The point is that the vertical and horizontal components of motion can be separated out, and that all bodies on Earth are subjected to identical vertical acceleration by gravity no matter how fast they're moving horizontally (assuming there's no lift involved).

 

[Trekker4747]

Naturaly, the morons on the MB Discovery website are arguing that the Mythbusters got this one wrong and that they reached the wrong conclusions. They're also arguing that the 30-some millisecond difference between the "landings" is enough to say that the bullets did not hit the ground "at the same time." (Even though that's well within any margin of error.)

As always, they're dead wrong too. There's some oddities with the way it was tested -for example the dropped bullet should've started dropping when the fired bullet left the barrel of the gun not when the trigger was pulled (since the bullet would be supported by the barrel of the gun and thus not subject to gravity.)

But, still, science and reality is on the Mythbusters' side on this one. Fired bullets are subject to gravity equally as dropped ones, fired bullets cannot gain any lift and thus have no way of staying in the air.

The 30-some millisecond difference is an insignificant ammount of time, faster than the human eye can see, and within the margin of error to account for the oddities of testing this.

A dropped bullet and a fired bullet hit the ground at the same time.

 

[Roger Wilco]

In my opinion 30 milliseconds would be a significant discrepancy that could possibly be explained by the aerodynamics of the bullet or something, if the testing setup had been really accurate, which it obviously wasn't.
If they had wanted to be extra nitpicky, they could have possibly just called it "plausible" instead of "confirmed", but if the physics are that clear and the test is that close - who cares. (except the nutcases in the Mythbusters forums of course)

 

[iguana_tonante]

At first reading the OP I thought they had fired the bullet to the ground.

 

[John Picard]

 

[UssGlenn]

Knocking your shoes off is relatively, easy, lots of mass there. Socks are tricky. I'm surprised they didn't mention people who have been hit by lightning, should be plenty of confirmed cases of shoes and socks blowing off and people surviving.