I recently watched Neil deGrasse Tyson explains modern airplanes doing turns and how the fluid level wouldn’t change inside the cabin when turning.
Video: https://m.youtube.com/watch?v=3SCxKTnC5YE
I’ve tried observing this myself and it didn’t always work as described. Reminder: you should still hang on to your drink just in case.
The comment section below the video mentions something called a “coordinated turn”.
What is it? When do pilots perform coordinated turns? Presumably a set velocity is required to achieve this for a given banking angle?
In: 2
Do you remember the term centrifugal force? We can have a whole discussion about why it’s called a fictitious force later if you’d like, but essentially, things accelerating (in physics, a change of direction is still considered acceleration even if you’re not changing speed. We can talk about that too if you’d like) feel a new force
No idea which came first, the centrifuge or the force with its name, but you can imagine a centrifuge which spins reeeeeally fast to push everything outside. Just like when you take a sharp corner at speed, you feel a force pulling you to the outside of the turn. Turn left, you get pulled right. Turn right, you get pulled left. It’s your body trying to stay on the corse it’s already on, but the car is moving underneath you… more or less.
We (by we, I mean all things that have mass) have no detector that can pull out the force of gravity (sigh, this is going to take all day if I keep offering to talk about things I’m more depth… gravity isn’t really a force either, just ask if you’re curious) from any other forces. As far as our mass is concerned, the force that’s pushing on us is just an average of all the forces. If gravity is pulling you down and centrifugal force is pushing you to the right, then the average force is diagonal down and to the right.
But what is down anyway? We have a pretty good idea, or so we think, but we live on a sphere (ok, of for some strange reason, you don’t believe that, let’s have another discussion. But just pretend we do). Down changes depending where on Earth you are. So what is a physicist’s definition of down? Is it the direction of local gravity. Gravity always points to the center of earth (mass center, not geometric center…. whatever, just ask about anything you like at this point. I’m ready for it.) But remember, our mass doesn’t know gravity from any other force. So if you’re inside a plane without a reference of where ground is (maybe your window shade has been closed, or you’re an unconscious body of liquid fuel who doesn’t even know what the ground is), then your body can only tell you the direction of the average force. That’s down for all you know.
There’s a video I’ve seen. I’ll try and find it and link it so come back in a bit if it’s not here. A guy is inside one of those spinning carnival rides. You’re supposed to lean against the wall to stay safe, but he actually stands. And he’s standing at a super extreme angle because his ‘down’ is different than your down. When spinning a drink, the liquid always wants to go ‘down’ but down changes while it’s spinning because the majority of force comes from the spin vs gravity like normal. (Edit: (https://youtube.com/shorts/SUzeCGTSJIg?si=YF1ub0-MIarpQEHB) just FYI. It doesn’t end well, so don’t try this one at home. Edit 2: [maybe a better video](https://youtu.be/RpQx204BJ7A?si=NvYUkoVpvxniRxjf) there’s a point in here where he actually dangles by the rafters. As you might be familiar, if you hang from something, it’s really hard for you legs to go anywhere but ‘down.’ That’s why Olympic gymnasts on the hanging rings have to be in such phenomenal shape to do the things they do)
When making a turn, the plane experiences some centrifugal force which changes the direction of down. The plane tilts in order to point the bottom in the new ‘down’ direction. The fuel inside doesn’t know the difference and remains perfectly level. Ta-Da!
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