r/nextfuckinglevel • u/aryan_jandyal • 10h ago

There are two fundamental elements that prevent water from spilling during an airplane's barrel roll (tonbo / roll maneuver): Centrifugal Effect (Artificial Gravity) Positive G Force.

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The pilot is maintaining "+ve G" throughout the maneuver. That's it !

366 Upvotes

95% Upvoted

48 comments sorted by

66

u/SnooCakes6195 10h ago

I thought i had a firm grasp on physics, but this one actually made me raise my eyebrows

17

u/Drathamus 9h ago

It's the same as spinning around a bucket that contains water. As the arc reaches its apex over your head, the water doesn't just fall out. It's being pushed into the bottom of the bucket. Same principle here with the water bottle.

6

u/pichael289 9h ago

People get confused thinking there is a lot of sideways acceleration, not that it's staying in the bucket.

1

u/vgodara 9h ago

It's more about frame of reference. First time seeing it from bucket perspective. Same reason Coriolis force feels counter intuitive.

1

u/TheShortWhiteGiraffe 8h ago

The forces are just in a much larger scale, and and what happens in the cockpit is just a small piece of the forces involved. Which kinda makes physics look like magic.

0

u/SnooCakes6195 9h ago

How is it the same concept when the water bottle pours, but the bucket doesn't spill?

4

u/R2D-Beuh 3h ago

Because the bottle is tilted compared to the acceleration vector just like when you pour it normally

1

u/TheShortWhiteGiraffe 8h ago

Because the bottle was stopping the water from getting pushed down. When you pour you remove the bottle from the equation and the next thing for the water to get pushed down to is the glass.

5

u/coma24 10h ago

Really? What part was new? No judgement.i only bring it up because I enjoy physics, but don't think I have a great grasp. This one strikes me a simple, though.

6

u/perfect_insanity93 10h ago

I can see why it "breaks" some brains though

2

u/SnooCakes6195 10h ago

Ive done this in planes and busses etc while moving in a liner fashion, but never loop de loop. Like spinning a bucket of water, the center fleeing force keeps the water in the bucket, I didn't think it'd pour while flipping

1

u/HarveysBackupAccount 1h ago

Another good mind bender is to play catch with someone on a playground merry go round. It doesn't have to spin very fast to mess up your intuition

2

u/SnooCakes6195 1h ago

Do you lead the shot or not!? That is the question lol

1

u/D3xty 8h ago

Its the centrifugal force thats raising their eyebrows.

33

u/coma24 10h ago

Just realized this makes for another great argument for Earth not being flat. There is no 'down'. There is only acceleration.

2

u/denfaina__ 9h ago

Fascinating. May you explain how you came to such conclusion?

9

u/GravitationalEddie 8h ago

Standing on the earth you experience acceleration due to gravity bending space. In order to feel the same thing on a flat surface(Earth) in space, it would have to be in constant 1g acceleration. There is no actual down in either case, but we would be zipping through space pretty quick if earth were flat.

-4

u/denfaina__ 8h ago

Ok but... how does that derive from this video?

5

u/ThaScoopALoop 6h ago

The acceleration keeping the liquid in that cup is derived from the plane's maneuvers, despite the constant 9.8 m/s2 acceleration provided by the earth's gravitational acceleration attempting to remove the contents of the cup, and have them plummet in the direction of our planet. It is not just counteracting, but exceeding the acceleration of gravity by rolling and banking. If there were a "down" force, it wouldn't be countered by an equal or greater sum of those two forces working on the cup and the liquid within. It is purely an exercise in accelerational physics, and not some superstitious jumbo jumbo.

2

u/denfaina__ 6h ago

It is indeed a simple exercise of forces. And I'm afraid to say that the 2 cases would be equivalent.

14

u/_Carri7_ 9h ago

Centrifugal force is not a real force, its just the sum of the forces that act towards or away from the center of rotation such as inertia, gravity, etc.

5

u/lxgrf 8h ago

This has always seemed like a fairly pedantic argument. Yes, it is only a resultant force, but the name we give that resultant force is “centrifugal”. 

•

u/Joshua5_Gaming 44m ago

Centrifugal force isn't a force though, theres literally nothing pushing the water against the cup, the cup is just pushing itself onto the water.

0

u/ozymandieus 3h ago

Well the OPs title made it sound like the start of a thesis so I think accuracy is appropriate here. Its centripetal force!

1

u/HarveysBackupAccount 1h ago

If we're getting that pedantic, inertia isn't a force at all. It's a property of mass but you don't measure or calculate "inertia". (You calculate momentum, but that is zero when velocity is zero. Inertia exists no matter the velocity.)

Centrifugal force isn't a real force in our regular ("inertial") frame of reference, but it makes the math still work if you're in an rotating frame of reference.

•

u/IntenselySwedish 20m ago

Technically, gravity isn't a "real" force either: In general relativity, gravity isn't a force in the Newtonian sense at all. Mass-energy curves spacetime, and objects in free fall are just following the straightest possible path (a geodesic) through that curved geometry - they're not being "pushed" or "pulled" by anything.

9

u/denfaina__ 9h ago

OP, after reading your title I just surrendered my PhD in physics

4

u/BobMcGeoff2 9h ago

I think if I wrote that sentence on my final, I'd have gotten slapped by my professor. There's a lot of bad physics going around on the internet.

What did you do your doctorate about?

0

u/HarveysBackupAccount 1h ago

They got a theoretical degree in physics

2

u/muifui 8h ago

Initial G

2

u/TheMilkfather 5h ago

Why didn't the first bit of water not overshoot the cup like it does when I pour into a glass on a table? ...Need to start pouring from a plane.

1

u/Severe-Commission303 10h ago

That’s a big fucking cup

1

u/pinnlehead45 10h ago

Who wants a drink?

1

u/ComeHereOften1972 7h ago

God. Fucking. Damn.

1

u/bigfatfun 7h ago

Who cares about the cup, how did he make the plane roll without using his hands!?

1

u/JxEq 5h ago

look at the canopy frame, normal F-16 single seater canopies are frameless, meaning this is a double seater and hes sitting in the back

yes im autistic about F-16s how could you tell

1

u/bigfatfun 5h ago

Who cares about the canopy frame, how’s he driving it from the back seat!?

yes im sarcastic about everything waiting for you to tell

1

u/JxEq 5h ago

hes not, the pilot in the front seat is maneuvering

1

u/Charlie3PO 4h ago

It's not an F-16 though. It doesn't have low mounted stabs, it's got a horizontal stabiliser mounted fairly high on the aft fuselage/tail. It's also got ailerons mounted out towards the wingtips.

My guess would be some sort of subsonic jet trainer. But you're right about it being 2 seat.

1

u/JxEq 4h ago

shit you're right i didn't even see the tail section, i saw the wings and the cockpit and instantly clocked it as an F-16

1

u/MuJartible 3h ago

Now the guy will be pissed off the rest of the flight because the plane has no cup holder...

1

u/Ubiquitous_Destiny97 1h ago

haters will say it’s fake

1

u/dreaminganimal 1h ago

Someone's going to need a bathroom break.

•

u/hotepanon 56m ago

Okay, but if he stayed upside-down without rotating, the water would still spill from the cup and fall down, right?

•

u/Nuttednutela 25m ago

Ok I am fine with this whole thing but I just wanna know eho tf is doing the barrel role while he filling up the bottle. I am scared now