Mythbusters S07E12 10/7/09 "Knock Your Socks Off!"

[Jonathan_S]

I loved watching Adam and Jamie verify the bullet drop myth. Setting it up so we could see the two bullets hit in the same frame was very cool.

I only wish they'd have a bit better shot from that high speed camera (better angle, more lighting, higher frame rate). But there were probably worried about shooting the camera :D.

Still very cool.

[verdugan]

Still very cool.

+1. I liked how Jamie was so into the myth that he even made a prediction.

The blow your socks off was kind of lame. Explosions are cool, but it seemed a bit gratuitous.

[doom1701]

The bullet myth was really enjoyable...the socks one was just another stupid build team explosion.

I am rather surprised that the bullet fell to the ground after only 360 feet. Or was it yards?

[aintnosin]

The bullet myth was really enjoyable...the socks one was just another stupid build team explosion.

I am rather surprised that the bullet fell to the ground after only 360 feet. Or was it yards?

Feet. Handguns are pretty short-ranged weapons.

Of course, to really test the myth, you would need to try with a longer-ranged weapon, say a .50BMG sniper rifle, where the curvature of the earth would enter the equation.

How you would test this scenario, I have no idea.:)

[nataylor]

The bullet myth was really enjoyable...the socks one was just another stupid build team explosion.

I am rather surprised that the bullet fell to the ground after only 360 feet. Or was it yards?

It was feet.

Let's do some calculations.

height = .5g*t^2.

I forget what the measured the time to be, but I do remember they placed the gun 36 inches above the floor. So, solving for t:

36 inches = 0.9144 meters

t^2=0.9144/(.5*9.8)
t= 0.432 seconds.

The bullet traveled 360ft in .432 seconds, which puts its velocity at 833ft/second, just about exactly what you'd expect from that gun.

[nataylor]

Feet. Handguns are pretty short-ranged weapons.

Of course, to really test the myth, you would need to try with a longer-ranged weapon, say a .50BMG sniper rifle, where the curvature of the earth would enter the equation.

How you would test this scenario, I have no idea.:)
Even over 360ft, the curvature of the earth did come in to play (though I don't think they mentioned it). There would be a difference in height of about half an inch. That's good for about a 3 millisecond difference.

[flatcurve]

I really liked the bullet myth too. I can totally see that segment being played in high school physics classrooms around the country.

[aintnosin]

Even over 360ft, the curvature of the earth did come in to play (though I don't think they mentioned it). There would be a difference in height of about half an inch. That's good for about a 3 millisecond difference.
Within their range of error. Over about 500 yards, the curvature amounts to almost 3 inches. Suddenly, we're talking about a non-trivial distance.

Again, I have no idea how to test that scenario.

[vertigo235]

Even over 360ft, the curvature of the earth did come in to play (though I don't think they mentioned it). There would be a difference in height of about half an inch. That's good for about a 3 millisecond difference.

Your assuming the floor in that building matched the curvature of the earth.

[nataylor]

For 500 yards, you'd need a muzzle velocity of 3472ft/s. That's getting up there. You'd actually want to go to a smaller caliber round for that kind of speed.

[nataylor]

Your assuming the floor in that building matched the curvature of the earth.

They said it was perfectly level, so it'd have to match.

[aaronwt]

I loved watching Adam and Jamie verify the bullet drop myth. Setting it up so we could see the two bullets hit in the same frame was very cool.

I only wish they'd have a bit better shot from that high speed camera (better angle, more lighting, higher frame rate). But there were probably worried about shooting the camera :D.

Still very cool.

I didn't think this was a myth, I thought it was physics that proved it?

[SleepyBob]

They said it was perfectly level, so it'd have to match.

If the floor is level, then that means it doesn't match the curvature of the earth. :confused:

[nataylor]

If the floor is level, then that means it doesn't match the curvature of the earth. :confused:

You and I must have different definitions of "level." To me, a "level" surface is one such that the force of gravity points directly down at any point on that surface. Place a ball anywhere on that surface and it'll stay put. Your definition leads to very large surfaces where you can place a ball and it'll roll away, because gravity isn't perfectly perpendicular to the floor.

[SleepyBob]

You and I must have different definitions of "level." To me, a "level" surface is one such that the force of gravity points directly down at any point on that surface. Place a ball anywhere on that surface and it'll stay put. Your definition leads to very large surfaces where you can place a ball and it'll roll away, because gravity isn't perfectly perpendicular to the floor.

Hmm. I see your point.

[Jonathan_S]

I didn't think this was a myth, I thought it was physics that proved it?
Myth was the wrong word; something I thought but didn't express well. (Although that half thought did lead me to say "they verified" rather than "they tested")

Just because something works in physics thought expiriment land it doesn't mean that it's easy to replicate in the real world. It was cool seeing how close it matched without exotic test conditions*.
(Yes, they were doing tricky thinks to syncronize the bullets, but that was for the sake of the video. Like Adam indicated, the experiment would have worked even with a delayed bullet release, because you could time each motion independantly. It wouldn't look as cool, but it would show that the physics were correct)


* Exotic: like having to do the testing in a vacuum. (For example you do need a vacuum chamber to replicate the "heavy objects don't fall faster than light objects" experiment, unless you're very careful picking test objects with matching terminal velocities)

[wmcbrine]

Over 362 feet, for all practical purposes, the Earth is flat.

Kari is huge! :) I think this is the first time she's mentioned her pregnancy in the show ("the little Mythbuster").

For some reason, my TiVo started recording the midnight showing, even though it had already recorded the 9pm airing.

[nataylor]

Over 362 feet, for all practical purposes, the Earth is flat.Well, if by "practical" purposes, you mean half an inch doesn't count, then yes. :)

[jbernardis]

For some reason, my TiVo started recording the midnight showing, even though it had already recorded the 9pm airing.

Mine recorded both 9:00 and midnight as well. Don't know why - must have been bad guide data.

[alansh]

Kari also mentioned it in the curving bullets episode, about her bulletproof vest "protecting for two".

I still wanna see the missing socks myth.

[vertigo235]

You and I must have different definitions of "level." To me, a "level" surface is one such that the force of gravity points directly down at any point on that surface. Place a ball anywhere on that surface and it'll stay put. Your definition leads to very large surfaces where you can place a ball and it'll roll away, because gravity isn't perfectly perpendicular to the floor.

Yeah I'm pretty sure when they level a building they would probably use a laser leveler or water leveler or such so that everything went together properly. If no they would have to account for the curvature as they built up.

For the purposes of this test I guess "flat" would have been a better description than "level"

[vertigo235]

Actually I think that if they used a water leveler it probably would account for the curvature, hmmm.

[nataylor]

Yeah I'm pretty sure when they level a building they would probably use a laser leveler or water leveler or such so that everything went together properly. If no they would have to account for the curvature as they built up.

For the purposes of this test I guess "flat" would have been a better description than "level"

Given the age of this particular building, I bet they didn't use a laser level.

Also, a laser level and a water level will give different results. A laser will always shoot in a straight line, gravity has no effect. But a water level takes gravity into account. If your water is at 36" off the ground in one location, it'll be 36" off the ground in a location a mile away, even though a laser level will be ~43" off the ground a mile away.

Edit: I see you slipped your comment in there while I was typing. Exactly right.

Also, I think this building used a poured concrete floor, which in general is going to follow the curvature of the earth. They'd have to go out of their way to make it not follow.

[vertigo235]

Well maybe that's why it was 35 miliseconds off! heh

[YCantAngieRead]

I completely misunderstood the bullet myth when they were describing it. I thought they meant shooting directly into the ground.

Guess I need to pay more attention.

[MarkofT]

I completely misunderstood the bullet myth when they were describing it. I thought they meant shooting directly into the ground.

Guess I need to pay more attention.That's the impression my wife had until they started showing the tests. It's probably dependent on your like/dislike of high school physics classes. Or just the lesson plan of the teacher in your high school physics class.

[Jonathan_S]

Given the age of this particular building, I bet they didn't use a laser level.

Also, a laser level and a water level will give different results. A laser will always shoot in a straight line, gravity has no effect.nitpick. gravity will have no practical effect on a laser over distances practical on earth given earth's gravitational field strength.

But try shooting one past a black hole (caution do not try this at home) and watch gravity have it's way with the laser.

[windracer]

I completely misunderstood the bullet myth when they were describing it. I thought they meant shooting directly into the ground.
I thought that at first too. :o

[jebbbz]

I wondered a bit about how they mounted the handgun. It was fixed in place to prevent rearward movement but they did not control for muzzle flip. I assume it had no practical effect on the outcome because it looked to be a 5" barrel on the gun but in theory muzzle flip would cause the bullet to exit the muzzle at a slight upward angle.

(I have never tried to calculate the answer but mention here that the curvature of the earth would be noticeable over a bit more than the length of a football surprised me. What did the Germans have to allow for with the Paris Gun in WWI, -- say 75 miles?)

[nataylor]

(I have never tried to calculate the answer but mention here that the curvature of the earth would be noticeable over a bit more than the length of a football surprised me. What did the Germans have to allow for with the Paris Gun in WWI, -- say 75 miles?)

Rule of thumb is 7" of drop per mile. So that'd be about 44 feet.

[brianp6621]

I wondered a bit about how they mounted the handgun. It was fixed in place to prevent rearward movement but they did not control for muzzle flip. I assume it had no practical effect on the outcome because it looked to be a 5" barrel on the gun but in theory muzzle flip would cause the bullet to exit the muzzle at a slight upward angle.

(I have never tried to calculate the answer but mention here that the curvature of the earth would be noticeable over a bit more than the length of a football surprised me. What did the Germans have to allow for with the Paris Gun in WWI, -- say 75 miles?)

Well they did verify that the bullets were shooting level/parallel to the floor before running the test, so it would seem to rule out that they were experiencing any upward trajectory due to muzzle flip.

[USAFSSO]

I guess the guys are on The Late Late Show w/ Craig Ferguson on Thur the 15th.

[sushikitten]

I still like this show, but am getting SOOOO tired of the big bang explosions just for explosions sake. I now fast forward through them.

[wmcbrine]

I still like this show, but am getting SOOOO tired of the big bang explosions just for explosions sake.+1

[nataylor]

Whereas I would be happy to watch a show that was nothing but explosions. :)

[MarkofT]

Am I the only one that noticed Adam riding an electric unicycle?

[nataylor]

Am I the only one that noticed Adam riding an electric unicycle?

Noticed that, too. Wonder if it was self-balancing like a Segway.

[mchasal]

Noticed that, too. Wonder if it was self-balancing like a Segway.

Looks like it:

http://www.facebook.com/pages/Focus-Designs-Inc-SBU-Self-Balancing-Unicycle/118834514301

http://focusdesigns.com/sbu-gallery/

[netringer]

...For some reason, my TiVo started recording the midnight showing, even though it had already recorded the 9pm airing.

Mine had the same episode on the To Do list for today or tomorrow. Something on the schedule confused TiVo.

[wmcbrine]

Yeah, mine too. It was going to record it a third time.

[morac]

Mine had the same episode on the To Do list for today or tomorrow. Something on the schedule confused TiVo.

The original air date is listed as October 23 (or around there), that's what's causing the issue.

[Frylock]

Yes, enough with the explosions already! Blowing stuff ip to just blow it up is BORING at this point.

[mattack]

Whereas I would be happy to watch a show that was nothing but explosions. :)

OK, it's not quite nothing but explosions, but I suggest you watch "Destroyed in Seconds".

[mattack]

I loved watching Adam and Jamie verify the bullet drop myth.

Both Adam & Grant have sent out tweets about criticisms of this episode.. I haven't watched it yet.. http://dsc.discovery.com/videos/mythbusters-the-combustion-chamber.html

Though I don't remember the exact numbers, it seemed to me wrong that they considered it 'confirmed'. It seemed like they got the bullet fire and bullet trop to within (MADE UP NUMBER) 1/3 millisecond.. But then the actual discrepancy in times between landing times of fired and dropped was several times that???