Questions tagged [lift]

Lift is the aerodynamic/hydrodynamic force on a body moving through a fluid that opposes the force of gravity. DO NOT USE THIS TAG for elevators. For aerostatic/hydrostatic lift in fluidstatics use the [tag:buoyancy] tag instead. For EM forces use the [tag:levitation] tag instead.

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249
votes
14answers
70k views

What really allows airplanes to fly?

What aerodynamic effects actually contribute to producing the lift on an airplane? I know there's a common belief that lift comes from the Bernoulli effect, where air moving over the wings is at ...
20
votes
3answers
12k views

Does a wing in a potential flow have lift?

I have a hard time understanding whether or not a wing placed in a potential flow, assuming there is no viscosity and no friction with the wing, will produce a lift. I've seen several contradictory (...
13
votes
5answers
5k views

How much effect does the Bernoulli effect have on lift?

I understand that the Bernoulli effect is a flawed explanation for the cause of lift, and does not cause much at all, but how much? Is there any experimental data on the force caused by the ...
4
votes
1answer
371 views

Do atmospheric physics prevent hot air balloons from ascending over 60,000ft?

I was reading the altitude records for hot air balloons on Wikipedia, and noted that the max hot air balloon altitude was about 60,000ft. It didn't really say if there was a reason why. I know that ...
45
votes
2answers
52k views

How can airplanes fly upside down?

I've read many times, including here on this very site that the commonly known explanation of flight is wrong, and that airplanes can fly because the shape of their wings deflects air down. This makes ...
2
votes
3answers
2k views

Are the hypotheses of the Bernoulli equation satisfied for a bird or airplane wing at low Mach number?

A previous question by David Zaslavsky was a request for a broad, "how things work" type of explanation of the lift of an airfoil. The answers given there are enlightening, but don't address a more ...
10
votes
2answers
11k views

Calculating the force required to lift a weight with a screw

I am trying to learn physics by myself as I do not have a good teacher at school. I've been reading Feynman Lectures on Physics and I can't figure out how he found out this number. Here is an excerpt ...
2
votes
2answers
3k views

Do wind turbines convert the kinetic energy of air?

It is often said that wind turbines convert the kinetic energy of the wind into electricity. But in respect to horizontal wind turbines with airfoil shaped blades this is imho not the case. Wind ...
-5
votes
5answers
147 views

Does the engine provide the lift of the aircraft?

In the absence of the effect of natural wind, a stationary aircraft will not move without the thrust of the engine, there will be no velocity without movement, and there will be no lift without ...
10
votes
4answers
24k views

How does the 'water jet pack' work?

So I was cruising around at YouTube and saw this sweet video, and as I was watching started to wonder: "How is this possible?". For a little bit of background, in case you decide to not watch the ...
7
votes
4answers
25k views

How much lift does the average latex helium filled party balloon produce?

How much lift does the average helium filled party balloon produce? (not including any extras like ribbon string)
2
votes
2answers
1k views

Why does a rocket spin during launching

Why does a rocket spin during launching? https://www.youtube.com/watch?v=BuPY5l45UC8
8
votes
3answers
11k views

Is Magnus effect a corollary of Bernoulli principle?

Magnus effect is commonly explained using Bernoulli principle. However, taking the lift on a rotating cylinder as an example, the velocity difference is caused by the extra work done by the rotating ...
8
votes
1answer
9k views

What is a Physically Accurate Explanation for the Kutta Condition?

Countless arguments between highly intelligent people have been waged (on this very site in fact) as to exactly how lift can be explained in an experimentally and mathematically rigorous way. Taking ...
4
votes
3answers
7k views

How much lift does an airplane get from its wings, vs the rest of the airframe?

Consider a big commercial airliner, like a 727, 747, or a 787. At cruising altitude, under standard conditions, how much of the lift of the aircraft comes from the wings, and how much from the rest ...
12
votes
1answer
3k views

Why exactly does a boomerang return back to the thrower?

I was always intrigued by the phenomena that govern the returning back of a boomerang to the thrower. Even if it is dependent on various factors such as velocity, aerodynamics, wind resistance and ...
4
votes
4answers
18k views

How is lift generated due to Coanda effect?

I can understand the generation of lift via Newton's 3rd law but I cannot understand via Coanda effect. I watched a video on YouTube that said that for the upper side of the aerofoil the pressure will ...
5
votes
2answers
698 views

Is it possible to fly like a bird using semi-motorized wings?

On his website http://www.humanbirdwings.net/ the dutch engineer Jarno Smeets claims to have successfully build a set of 17 m^2 bird-like wings from material of a kite. It is claimed that it uses ...
-1
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2answers
3k views

Why does the higher pressure of air underneath an aeroplane wing keep it flying?

With aeroplane flight, the wings are shaped so that the air that goes over the top of the wing has to travel faster than the air that goes below the wing. This means that the air below the wing has ...
-2
votes
3answers
96 views

Suppose we do this experiment in a vacuum, will the small pieces of paper behind the bottle be blown? [closed]

Put a lit candle behind abottle. If you blow on the bottle from the opposite side, the candle may goout, as if the bottle was not there at all. Explain the phenomenon. My vacuum here refers to the ...
9
votes
2answers
5k views

Could some design of a propeller be used in both air and water?

Propellers in water are smaller in diameter. They also move more slowly. On the other hand, aircraft propellers are larger in diameter, have narrower blades and operate at very high speeds. An ...
8
votes
1answer
1k views

Could the phenomenon of vortex bursting be exploited to reduce wake turbulence?

One of the classic stories in the annals of aerospace engineering is the development (and subsequent redesign) of the F-18 and its Leading Edge Extensions (LEX) due to fatigue problems, problems that ...
4
votes
2answers
6k views

Integrating pressure over a surface

Consider the 2D airfoil below. (source: gsu.edu) In engineering (and maybe physics) you will often see something like the following as an expression for the pressure force acting on a surface (in ...
4
votes
5answers
2k views

What principles does an air glider use?

I just saw this video which was kind of nifty. What principles govern this? Is it simply that 700 lbs of air pressure are exerted from that little 1 HP blower? What would you have to take into ...
1
vote
2answers
536 views

What does centre of lift depend on?

I've read in many places that centre of lift is about quarter chord of the wing and that post-stall lift (the part developed on lower surface) has centre midchord. The later makes sense; the pressure ...