Monday: Jimmy-boy
Tuesday: For Science!
Wednesday: Yahtzee!
Thursday: No Right Answer to this one

first half of the week: finally: check!

also, it was really surprising The Makers actually gave that scene some thought :D

Crusnik:

monev44:
I like this. My one remark on this episode would be. Yes they can survive the impact with the water, but what about the impact with the bottom of the lake? how deep would the water have to be for them to slow down enough so they don't impact the lake bed with more then a survivable G-force?

F = (1/2)*rho*Velocity^2*Surface area*Coefficient of drag

F = weight of tank = 22.25 tons = 197812.02 Newtons

sqrt(197812.02/.5*1000*2.69*2.55*0.8)=8.49 m/s or 18.9934 mph.

It would be perfectly fine.

that 8.49m/s would be the terminal velocity while in the water yes? That's all well and good. but my question is more along the lines how far down would they travel in the time it takes the water to slow them down from their entrance velocity to the new water terminal velocity? If the lake is only 20 feet deep they are almost certainly screwed. So what's the minimum depth necessary? assuming fresh water, and room temperature. (they didn't look cold.)

Joos:
Somewhat interesting detail: The only reason people survive crashes in cars at 33mph, is the fact that you have two things: A stiff crash cage around the occupants and crumple zones in front that eat up the energy and reduces the pulse that goes into the occupants from the extremely high deceleration.

Now, I don't know what sort of a pulse you would get from impacting water at 33mph, but I presume it would be a lot higher than you'd expect. And, since a tank doesn't have crumple zones, pretty much the opposite; the whole impact pulse will be transferred into the occupants squishy little bodies. This will most likely end in severe bodily harm and probably death.

But hey, it's a movie right?

well they said they would have hit with 3Gs of force.. , not only is that survivable, as long as you have a seat belt its an amusement park ride.

Anakinnnn:
snip

Don't worry too much, I'm pretty sure it soon will, everyone needs their time with it. And don't worry about coming across as dorky, this is a gaming site, we're all a bit awkward. Keep up the good work. Just keep making interesting episodes, I think you'll get the gist and be more comfortable.

rvdm88:
A few things were left out though:

What would be the tensile strength of the parachute cables?, would one cable be able to carry an entire tank?
Also The chutes werend deployed instantly, so im wondering, would the speed at wich the parachute deployed not rip the chute to shreds?

Another thing that im wondering is, would the crew be able to handle tankshells in such a orientation/stress?
or is the tank outfitted with a automatic loading system, and if so, can this mechanism work in a vertical orientation?
The last thing im wondering about is, how plausible is the pendulum motion that they create by firing sidewards.

Its an autoloader. They are fairly reliable from what I know, should still work with the tank doing acrobatics though I doubt anyone will be able to test this.
Another thing I found is that it load 12 shells per minute maximum, so it would not be able to fire every 3 seconds.

Awesome show guys. Could you try and have all the figures in both imperial and SI units? The imperial units mean very little to me beyond mph. I took physics at A level so this show is extremely interesting to me!

I already love these guys. looking forward to more.

darksakul:

Davey Woo:
They said that the tank cannon is fired roughly every 3 seconds during freefall. Did you check to see if it was possible to fire, reload and fire again in that timeframe?

I know as it was proven that firing the gun didn't have much of an effect on the tank's speed, but would be interesting to see if they had researched that as well.

While I can't provide an official source, since the actual reload times are classified, as demonstrated in many US military films/ videos to the public tanks do have a 3 shots per second reload time.

For those who are thinking the armor will break, the cannon be damaged or you know the material the tank's armor is?
This is also wrong as the exact composition of the armor and the materials in the cannon are also classified as Top Secret.
How top secret were talking about, I was in the military and all I ever found out is the armor is not aluminum, and it much more tougher than any civilian vehicles. You can't even know about (or see) the cross section to that armor without being interrogated as a national security threat. Same armor as a Prius my ass.

Is the Tank air tight? Well there are NBC (nuclear, biological and chemical) air filtration systems on board, in order to make the air breathable in a hostile environment the tank has to be air-tight. So its plausible that the tank can survive a short time under water.

The Prius comparison was an exaggeration, obviously ;)

What I looked up myself came from various sites, they seemed roughly consistent about their information but it could of course be they all drew from the same misinformation, such is the risk of using the internet.

I also never mentioned it is armored with aluminium, but that the hull in constructed with it. Its a 19 to 25 ton light tank, while a modern MBT weighs between 50 and 65 tons. Its not hard to tell it compromised on its protection quite a bit, even without knowing all the classified details.

That was awesome. Very cool show and informative too!

I actually loved that. Looking forward to more.

Wow, i have to repeat what i said yesterday:
Great show and i can't believe you took the time to answer our questions, tanks ! (pun intended)

yngi:
math is hard

Let's go shopping! :)

OT: Great new series, the math nerd in me felt great joy seeing that the details weren't kept under the rug.

This is fantastic! And I like that you started with something plausible. Just pointing out flaws in hollywoood logic, instead of successes, is way too easy.

an awesome debut video. although im suprised no one has mentioned saintsrow 3 and tank skydiving

Assuming that the impact against the surface of the lake didn't kill them, assuming that the tank was an NBC variant, assuming that the impact didn't break any seals of that NBC variant, assuming the straps holding the tank to the platform had shattered, and assuming that the tank landed treads down on the bottom of the lake, assuming they had an electric drive system that didn't rely on external ventilation, they likely still would have died.

Because tanks do not operate well on soft ground.

This is what beat the Germans on the Eastern Front. Mud and snow. During the German offensive, the majority of German tanks became bogged down due to soft conditions because their tracks were too thin to allow them to effectively operate in those conditions. http://www.allworldwars.com/Effects-of-Climate-on-Combat-in-European-Russia.html Just like Napoleon before him, Hitler was defeated by the Russian weather.

Now the bottoms of lakes contain notoriously soft soil of extremely fine particulate size, referred to as silt. Silt particles are smaller than those of sand, which like sand, allows great amounts of silt to be transported in the air and water, which eventually settle, leaving thick formations on the bottoms of bodies of water.

Before someone wants to argue about modern vehicles vs WW2 era ones however, we can go and look up the very specifications that would cover the design of the M8, http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA433075 from which the traction specifications can be determined and http://cmfac.groups.et.byu.net/miller/cm411/basicsoil/key.jpg soil conditions can be determined. In the interest of me getting sleep, I am not going to bother calculating it out, if some intrepid individual wishes to attempt it, they are welcome to, I will gladly check their work tomorrow.

Another factor that has to be accounted for is the speed in water, which obviously is greatly reduced as water is a far more viscous fluid than air. This will negatively impact the traction capabilities on any given soil.

Cheers.

This series looks interesting, will be looking forward to more.

One suggestion: not all of us are good with math, it would help if you elaborate more perhaps with pictures or cgi along with the formulas.

What I'd like to know is could 1 parachute have held the tank without the tension breaking it off.

BehattedWanderer:
Okay, but how about the helicopter flip?

That has to be one of the funniest things ever xD

Seeems interesting althou I am nowhere smart enough to understant most, I got the point that it could be true :D

interesting video

Groenteman:
Nother edit: You used numbers from the 120mm rheinmetall gun, this is a 105mm gun.

This particular variant of the Buford ('Thunderbolt' AGS block II) was armed with a Rheinmetall XM-291 120mm gun with an autoloader. It was a technology demonstrator, so you could argue that the chances of coming across the only one ever made would be pretty slim, but that's neither here or there for this argument.

Fake laughter is fake.

Hope this series sticks around -- that was fun.

ok was pretty interesting its a pity that they used messed up units that mean nothing to me or anyone else out side the states really what's a foots per second really? and why not use SI units even in the states science is done in SI units

monev44:

Crusnik:

monev44:
I like this. My one remark on this episode would be. Yes they can survive the impact with the water, but what about the impact with the bottom of the lake? how deep would the water have to be for them to slow down enough so they don't impact the lake bed with more then a survivable G-force?

F = (1/2)*rho*Velocity^2*Surface area*Coefficient of drag

F = weight of tank = 22.25 tons = 197812.02 Newtons

sqrt(197812.02/.5*1000*2.69*2.55*0.8)=8.49 m/s or 18.9934 mph.

It would be perfectly fine.

that 8.49m/s would be the terminal velocity while in the water yes? That's all well and good. but my question is more along the lines how far down would they travel in the time it takes the water to slow them down from their entrance velocity to the new water terminal velocity? If the lake is only 20 feet deep they are almost certainly screwed. So what's the minimum depth necessary? assuming fresh water, and room temperature. (they didn't look cold.)

Good Questions.

Temperature doesn't actually matter, as water (being a liquid) does not follow the perfect gas law. Its density is not dependent on temperature so long as it remains in liquid state.
Without using calculus because I'm lazy ( I used Excel instead) it would take 624 meters to slow the tank down to it's minimum velocity of 19 mph. However, it takes only 100 meters to slow down to 20 mph and only 80 meters to slow to 21 mph. Again, this disregards any buoyancy which would only help to further slow the tank.
Considering that it is a mountain lake, as depicted by the scenery, it is fairly likely to be a deep lake, at least 50 meters, which would be enough to slow it down to around 23 mph.

RoonMian:
I never even considered that they were shooting down to slow themselves... When I saw the movie I thought they were shooting down to make the water in the lake unruly because moving water offers less resistance... Which, in hindsight, I guess makes about as much sense as using the recoil to slow them down.

This is what I thought too. I thought they were trying to break up the surface tension of the lake to make their impact easier. Most armored gun platforms can fire an armor piercing round or an explosive (HEAT) round, HEAT rounds have greater mass and explode on impact.

geier:
Great new show, i like it.

Question:
Wouldn't the tank be damaged when hitting the water ?
Especially the barrel ?

From what I gathered, no because the shape of the tank means the impact isn't instantaneous and it wasn't that large a force in the first place.

Nice job of starting with a bang. I do hope that you do TV as well as Movies. If you do TV would love to see some some Burn Notice stuff done here. One that always did bug me is, motor fu. The whole deal of using a motocycle to fight against each other. That always look like something that wouldn't involve any real physics.

Holy fuck.

I love this show already.

Mythbusters, but AWESOME.

The amount of math and physics gave me a massive boner. A science boner. Of science.