# 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 [buoyancy] tag instead. For EM forces use the [levitation] tag instead.

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### What is circulation, regarding a wing, and why does it happen?

I was wondering, in layman's terms, what causes circulation around a wing? I understand that flight is a combination of Bernoulli's theorem and Newton's third law. The Coanda effect and Kutta effect ...
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### Lift force equation of a rocket and Lift curve slope

I'm trying to determine the lift curve slope of a rocket to get the lift coefficient, using L/qA . the lift equation I'm using is thrust-drag-mgsin(alpha). to me this seems correct as it essentially ...
1 vote
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### Helicopter hover flight question

I'm an avionics technician and I work on helicopters. This week I was trying to explain where comes the lift force to some friends. I'm a self-learner but I have a poor physics school background. I ...
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### Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?

The JP Aerospace's Tandem airship achieved a record-breaking 28,982 meters for the highest airship flight. After reaching this height, can the helium balloon be used as a propellant, the same way if ...
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### Are drag and lift forces directly proportional to air density?

I'm trying to work out how air density changes displacement during takeoff and up to a height of 35ft. All the websites I find say that the coefficients of lift/drag are Yet I want to know whether I ...
162 views

### Antigravity force in powered precession gyroscope [closed]

I have an idea that a powered for rotation gyroscope with fixed precession can serve as antigravity engine. I also wonder of someone tried an experiment to prove that it does not work. The following ...
1 vote
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### Convert BLDC motor thrust in grams ($\rm g$) to Newton ($\rm N$)

I am making a quadcopter with takeoff weight equal to 2 Kg. Using thrust to weight ratio of 3:1 the required thrust per motor is 1500g. (No experimental thrust has been obtained for thrust.) Now I am ...
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1 vote
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### Stability of a crate lifted with a lifting beam and two slings when the center of gravity is above the attachment points of the slings

I have a hard time understanding the stability of a crate lift when using a lifting beam. Consider the system in the first figure, where a crate is suspended in two lines using a lifting beam. Presume ...
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### What happens to the distribution of the induced angle of attack, if we suppose the circulation distribution is constant?

Assuming the lifting-line theory, we know the circulation must go to zero at the tips of the wing. Therefore, I wonder if we can actually conceive such an idea as a constant circulation across the ...
1 vote
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### What is the weight of an object that accelerates upwards?

I belong to the aerospace community, and a basic concept among the people of this community is that an aircraft is called to be in 'steady flight' when the lift force balances out the weight of the ...
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### Can astronauts fly like birds in the space station?

Can astronauts fly like birds in the space station? The space station is microgravity, and astronauts can't walk. Can we design a pair of wings for astronauts to fly in the space station? What if the ...
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### Could super-heated gas allow for Dirigibles/Zeppelins/Balloons to go higher than 60 km of altitude?

Well, I don't know much about physics in general, so I hope I don't make too many misconceptions. So, from what I could read in this Wikipedia article, the balloon named "BU60-1" achieved ...
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### Airplane lift origin and cause? [duplicate]

How does an airplane get a lift? Is it due to the newton's third law or coanda effect or both? I am an amateur in this , kindly use simple terms.😅
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### How exactly does a fixed pitch wind turbine start from standstill/stall?

I might have a crucial gap in my understanding of the aerodynamics of a wind turbine but I am struggling to get my head around how a fixed pitch wind turbine can start spinning from a standstill? I ...
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### Can the UAV fly in the space station? Can birds also fly in the space station?

Can the UAV fly in the space station? Can birds also fly in the space station? Birds can bump around the space station.
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### Which is correct related to lift: Bernoulli's theory or Newton's theory? [closed]

I was trying to find out how exactly is lift generated. I came across Bernoulli's theory and Newton's theory. But I no where found which one is correct. Can someone help me out with this?
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### How do flat insect wings generate lift?

The traditional Bernoulli explanation of lift depends thoroughly upon a wing which, through differing geometry between the upper and lower wing surfaces, causes higher air velocity above and below, ...
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### Circulation around airfoil implies infinite kinetic energy, but where from?

The standard model for the circulation around an airfoil is $W(z) = C \log(z)$, which implies that the velocity around an airfoil moving through a 2D fluid at rest goes $\sim 1/r$ with increasing ...
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### If Bernoulli's Principle can only be applied to a streamline, how does it justify the pressure difference that causes lift

According to the Bernoulli's principle, an increase in the speed of a fluid causes a decrease in pressure. In the case of an aerofoil or aircraft wing, the speed of the fluid (air) above the wing is ...
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### Is the downforce of rain on airplanes negligible?

Is the downward pressure exerted by raindrops in even a strong storm on a lightweight aircraft negligible? Someone better informed may likely improve the following reasoning, cobbled together from ...
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### Would a rotating sphere placed within a pipe with air flowing through it experience a lifting force due to the Magnus Effect?

I am wondering if a rotating sphere placed with a pipe/duct with air flowing through the pipe will cause the rotating sphere to experience a lifting force due to the Magnus Effect. Moreover, if the ...
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### The lift of an airplane is similar to that of a balloon. It uses the density difference of air, right?

The lift of an airplane is similar to that of a balloon. It uses the density difference of air, right? The air density on the top surface of the balloon is low and the air pressure is small. The air ...
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### Can spinning increase lift of an air balloon?

If we spin an air balloon, the centrifugal force would cause it to expand, since it is directed outwards. Increased volume of the balloon would increase the buoyant force. Can this be used to ...
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1 vote
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### What is the difference between buoyancy and buoyant force?

We were solving this question, then the instructor mentioned like Buoyancy force is due to pressure difference, what does pressure difference has to do with upward force? Upward force should be the ...
1 vote
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I already asked the same question and got great answers but im also confused. One of the answers said that I can imagine that, because air over the wing has a higher pressure than the air right above ...
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### Correctness of a certain physical model for calculating the lift acting on a spinning and stationary frisbee

I just wanted to check if the fundamental physical principles of the following calculation of the aerodynamic lift acting on a rotating frisbee without translational motion, are correct. I assume a &...
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### What direction is aerodynamic lift in?

So I was researching about aerodynamic lift, in all the research I read it says lift is perpendicular to the flow direction. But in 3d space there isn't only one perpendicular vector to a given vector....
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### Why do curved flows accelerate?

So I’m a bit of a fluid dynamics nerd, but for a while now this has been bothering me. We know that wings produce lift in part because of the flow accelerating over the top of the curved wing, and as ...
1 vote
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### Possible for Magnus effect to overcome rotational phenomena?

I’ve noticed that when a moving, rotating disk is in contact with a surface, it curves the opposite way it is spinning (eg, a puck on a table moving forward and rotating clockwise would curve left). ...
1 vote
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### What is the reason for this lift force?

Refering to this closed question, I made a test using a fan, a styrofoam sheet and a scale as shown in the fig (a) and (b) Part of the weight of the sheet is supported by a rod close to the wall, and ...
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1 vote
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### Magnus effect -Direction of the resultant force experienced by the spinning ball

Consider this picture: This picture shows the effect of Magnus Effect experienced by a spinning ball in air. My text says the following: The figure shows the streamlines of air for a ball which is ...
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### Bernoulli and flight

Am not a physicist but Bernoulli's principle states that when fluids flow faster lower pressure is created, thus explaining lower pressure on the top of a plane wing... But in the case where the air ...
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### Trains - can aerofoils reduce friction?

Trains need energy to overcome friction at the wheel-rail interface during constant high speed speed running. Aerofoils on the roof could provide lift, reducing the friction and potentially saving ...
1 vote
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### Are the lift and drag force on a wind turbine blade responsible for torque development?

Is the lift and drag force on a wind turbine blade are responsible for torque development? I understand that the torque and thrust are the decomposition of the net aerodynamic force on the turbine ...
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### Is it possible to lift a bald person with an airstream? (Coanda effect and Bernoulli's principle)

Lately, a high school teacher called Bruce Yeany has been uploading some fluid dynamics demonstrations on his YouTube channel. Here's his first demo video using various objects like vegetables and ...
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### How much vacuum is needed to lift?

Just like a balloon of Helium lifts about 1.02g for being less dense than the air. Does the same principle applies to vacuum being less dense than air? And if so, how much can a ballon (1L) of vacuum ...
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### What is the bare minimum of air density you need to fly a helicopter?

How high will a helicopter be able to fly before the propellers have not enough air particles to achieve lift? What is the minimum air density needed to achieve flight with a helicopter? Could you ...
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### Modeling a 3D Wing -- Joukowsky Airfoils and Prandtl Lifting-Line Theory

I am trying to calculate the distribution of lift over the span of a rectangular, non-swept wing with a (constant) Joukowsky airfoil cross-section. The wing is rectangular in the sense that the chord ...
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### How did the derivative shift? (Turbojet Thrust Equation)

While deriving the Turbojet Thrust Equation this is what the author does $$F=m\cdot a$$ $$F=m\frac{\mathrm{d}v}{\mathrm{d}t}$$ $$F=\frac{\mathrm{d}m}{\mathrm{d}t}v$$ $$F= m^*\cdot v$$ (where $m^*$ is ...
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### Calculating rotor inflow ratio in a helicopter rotor

Disclaimer, this is not homework. I am trying to determine the amount of lift force that a rotor on a toy helicopter actually produces. With some googling, I've learned that the formula for this is: ...
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### Lift on Airplane wing

Why commercial airplanes use long, slender wings? Isn't it to maximize lift, we make the plane's wings as wide as possible?
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### Pressure Drag on a 2D Aerofoil even when no Separation of the Boundary Layer?

So if a 2D aerofoil is subjected to potential flow, then there isn't a boundary layer separation at any point with the surface of the object, and hence pressure remains constant at the front and back ...
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1 vote
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### Trying to calculate forces and torque

I am designing (in my mind) an accordian / scissor crane, but have little knowledge of calculating torque, fkg/cm etc. I've enclosed a sketch. I need to pull the apex of the triangles together to ...
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### Can the circulation around a wing be predicted (roughly) without the help of a computer? [duplicate]

This site already has several questions about how airplanes fly. Some of the answers do give useful insights, but the only real explanation I've found involves using a computer to solve the Navier-...
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### Can helium gas lift the bottle itself?

I came up with this argument: it’s possible that in the right circumstance helium would weigh more than the empty bottle. If I were to fill empty bottle full of helium can it lift the bottle in the ...
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### Can we make a drone fly on the Moon by using cylinders with compressed air (or cold helium)? [closed]

Suppose we want to make a drone fly on the Moon (the gravity on the Moon is 1/6 of that on Earth), only by making use of its rotors and air. The drone is as light as possible ($m_{min}(kg)$, has ...
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### Forces on a spinning ball

The drag force opposes the direction of velocity, and the lift force is perpendicular to both the drag force and the rotation direction. So if a tennis ball is rotating clockwise and moving to the ...
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### Wind tunnel experiment that measures lift (not the lift coefficient)?

Does anyone know of a wind tunnel experiment on a wing or airplane that measures the absolute amount of lift (not the lift coefficient); and demonstrates conclusively that the lift generate by a wing ...
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