The force on a body moving through a fluid that opposes the force of gravity.

learn more… | top users | synonyms

14
votes
2answers
1k views

Why don't rockets tip over when they launch?

Rockets separate from the launch pad and supporting structures very early in flight. It seems like they should tip over once that happens. Why don't they tip over? Is it due to a well designed ...
11
votes
3answers
2k 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 ...
0
votes
1answer
92 views

Quadrotor dynamical equations on center of propeller

I work on a quadrotor project. It is commonly wide dynamical model according to the center of quadrotor. However, I need quadrotor dynamic equations on center of one of the propellers. It seems very ...
1
vote
2answers
417 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 ...
1
vote
1answer
31 views

Velocity in the lift equation

What exactly is the nature of the velocity in the lift equation? I have read that it is the velocity of the aircraft, and I think I have read that it is the relative velocity of the air to the ...
1
vote
1answer
2k 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)
3
votes
3answers
1k 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 ...
98
votes
6answers
10k 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 ...
16
votes
2answers
7k 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 ...
1
vote
2answers
278 views

Forces on an aircraft - thrust, lift, drag, weight

I'm extremely sceptical about the wikipedia page on aircraft flight mechanics. When describing 'straight climbing flight', it says: lift is unable to alter the aircraft's potential energy or ...
7
votes
3answers
8k 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
5answers
3k views

Does it take significantly more fuel to fly a heavier airplane?

I was reading in the papers how some-airline-or-the-other increased their prices for extra luggage, citing increased fuel costs. Now I'm a bit skeptical. Using the (wrong) Bernoulli-effect ...
6
votes
2answers
629 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 ...
4
votes
5answers
839 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 ...
0
votes
1answer
148 views

Surviving Free Fall with the Help of Mr. Bernoulli

What is the best strategy to survive a free fall naked out of a jetliner at cruising altitude (ignoring temperature)? For instance, my strategy would be to streamline my fall so that my terminal ...
5
votes
4answers
273 views

Can a balloon be used as an anchor point for a pulley?

For a physics/ engineering contest, I want to use a large balloon as an anchor point for a pulley. This would allow me to raise and drop masses. However, in testing, when I pull on the pulley the ...
3
votes
3answers
432 views

Does launching a rocket in lower density air require more or less fuel?

Given two environments that are identical, except for air density (e.g. Cape Canaveral, but at Mount Everest's height), would launching a rocket require more or less fuel at the lower air density?
1
vote
3answers
126 views

How does the position of lift affect the stability of the lifted object?

Consider this example: Treat G as 10. The blue blocks provide lift of 10N, or -1KG. The red block has a weight of 20N, or 2KG. The black bar has no weight. All have their center of gravity in ...
13
votes
5answers
670 views

Is flying really easier on smaller scales?

In the book Playing with Planets, the author makes the following argument, pertinent to flying robots of the future: As it is, an important law of physics says that smaller organisms fly much more ...
2
votes
2answers
379 views

Forces on an airfoil

I'm building an airplane (Super Baby Great Lakes) and I'm wondering something about airfoils. In particular (this plane is fabric covered), I'm wondering about the lifting forces on the main wings. ...
-2
votes
2answers
307 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 ...
5
votes
2answers
571 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 ...
4
votes
4answers
2k views

Why do aircraft inner wings lose lift when turning?

first question here, so please be gentle! I'm reading an entry-level engineering course book and am currently up to discussion of aircraft design. There's one particular statement that is unclear to ...
4
votes
1answer
247 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 ...
3
votes
4answers
555 views

Could hydrogen liberated from water provide lifting energy which exceeds the energy it took to liberate it from water

I was thinking about Hydrogen balloons and that large ones which are used for weather balloons which sometimes go up to 100,000 ft (approx 30km). Then I was wondering, how much potential energy has ...
8
votes
1answer
2k 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 ...