Mark Drella

So, if you could visualize air going past an object moving through the air, or if you visualize a water moving past an object moving through the water, they literally look the same. So, for example, The Goodyear blimp is almost mathematically identical to a submarine.

Mathematically, you cannot tell the difference.

Mathematically, you cannot tell the difference.

Mathematically, you cannot tell the difference.

Okay, so just going back to your hand moving out of the car window, right?

Okay, so just going back to your hand moving out of the car window, right?

Okay, so just going back to your hand moving out of the car window, right?

The air needs to an area to push against, right? Pressure is the major way how fluids impart force to an object. So, for example, water rushing past a water skier, the water pressure under the skis is larger than the overall surrounding pressure. And that extra pressure on the bottom pushes up on the skier. Just like the air pressure underneath on the bottom surface of a wing pushes up

The air needs to an area to push against, right? Pressure is the major way how fluids impart force to an object. So, for example, water rushing past a water skier, the water pressure under the skis is larger than the overall surrounding pressure. And that extra pressure on the bottom pushes up on the skier. Just like the air pressure underneath on the bottom surface of a wing pushes up

The air needs to an area to push against, right? Pressure is the major way how fluids impart force to an object. So, for example, water rushing past a water skier, the water pressure under the skis is larger than the overall surrounding pressure. And that extra pressure on the bottom pushes up on the skier. Just like the air pressure underneath on the bottom surface of a wing pushes up

on the wing, and that holds up the airplane. So you need area. In fact, on very simple high school algebra, force is pressure times area.

on the wing, and that holds up the airplane. So you need area. In fact, on very simple high school algebra, force is pressure times area.

on the wing, and that holds up the airplane. So you need area. In fact, on very simple high school algebra, force is pressure times area.

Absolutely.

Absolutely.

Absolutely.

Okay, so again, the simplest explanation is you go back to your hand sticking out the car window. If you hold your hand perfectly horizontally, right, you won't feel a force. To get an upward force, you have to tilt your hand so that you present the bottom of your hand to the oncoming flow, right? That angle is called the angle of attack.

Okay, so again, the simplest explanation is you go back to your hand sticking out the car window. If you hold your hand perfectly horizontally, right, you won't feel a force. To get an upward force, you have to tilt your hand so that you present the bottom of your hand to the oncoming flow, right? That angle is called the angle of attack.

Okay, so again, the simplest explanation is you go back to your hand sticking out the car window. If you hold your hand perfectly horizontally, right, you won't feel a force. To get an upward force, you have to tilt your hand so that you present the bottom of your hand to the oncoming flow, right? That angle is called the angle of attack.

That will make the pressure on the bottom of your hand larger than on top. And that resulting pressure difference imbalance times the area of your hand is the lift acting on your hand. Exactly the same thing happens with an airplane.