wolverine asked in Science & MathematicsPhysics · 6 months ago

# Bernoulli’s principle explains why,?

a. Airplanes fly

b. Dead fish float

c. Liquid rises in a drinking straw

d. A hot air balloon rises.

Relevance
• 6 months ago

None of the above.

Bernoulli showed that a fluid on speeding up must gain a lower pressure.

A function of conservation of energy.

But this is not a good explanation for the function of a wing.

A plane can fly upside down.

A plane with a flat wing can fly fine.

The aerofoil provides efficiency by minimizing turbulent losses. However if you watch a plane on landing you will see that the wing is always at an angle to the direction of motion.

THAT is the key.

Momentum is conserved.

If you change the direction of the airflow then impulse = change in momentum

Ft = Mv

F = Mv/ t

Which is the same effect as standing in front of a fire hose and being knocked flat.

That can be observed if you have seen a stunt plane

• olivia
Lv 5
6 months ago

An increase in the velocity of a fluid that is accompanied by a decrease of pressure. Swiss scientist, Daniel Bernoulli (1700-1782), demonstrated that, in most cases, the pressure in a liquid or gas decreases as the liquid or gas moves faster. This explains in part why a wing lifts an airplane.

• 6 months ago

Bernoulli looks and sounds right, but is not correct

• 6 months ago

A is probably the answer that the person wrote the question is looking for, but it, too, is in fact wrong:

https://www.grc.nasa.gov/www/k-12/airplane/wrong1....

• dogsafire
Lv 7
6 months agoReport

Thank you!!! I've tried to explain why the Bernoulli explanation can't be right, but "everyone knows" the correct answer. I tried once with an airline pilot, hoping that he would have a better grasp of the physics. Nope. Bernoulli was all he would listen to

• oubaas
Lv 7
6 months ago

a) , definitely ...It is the change in pressure up and down the wings that determines the lift

• 6 months ago

https://www.yourdictionary.com/bernoulli-s-princip...

The information at the website above explains how the shape of an airplane wing affects the pressure the air exerts in the wing. Since the top of the wing is curved, the space between the air molecules is greater than the space between the air molecules on the bottom of the wing. This difference of space causes a difference of air pressure. This difference of pressure produces a difference of force. As the speed of the airplane increases, this force increases. When the force exerted by the air molecules is equal to the weight of the airplane, the airplane will liftoff.

A is the correct answer.

• dogsafire
Lv 7
6 months agoReport

Bernoulli looks and sounds right, but is not correct

• ?
Lv 6
6 months ago

I think it's the first one. I saw Wild Wild West recently and by a strange coincidence, it spoke about Bernoulli.

It would have taken less time to Google this question than type it out. Now you have to wait for responses and sort through public nonsense to figure it out.

• 6 months ago

D-not correct, the differential in density makes hot air balloons rise

C- not correct, whetting make liquid rise in straws and differential in area.

B-not correct, fish have 'ballast bladders' that expel water when they die becoming positive buoyant.

A- correct, air moves faster over an airfoil with the greater distance of semi symmetry. faster air, lower air pressure.