# 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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### Should the weight of the lifting surfaces of an aircraft be deducted from The weight used to calculate the C of G of the aircraft?

If the aerofoils are creating lift they are doing the work to lift the helicopter. When the helicopter is hovering, the blades are carrying the weight of the entire ship. The forces on the aerofoils ...
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### Does the engine's thrust not contribute to the lift? [duplicate]

Does the engine's thrust not contribute to the lift? Here are my thoughts: There are two types of aircraft resistance, one is the resistance created to create lift, referred to as lift resistance, ...
145 views

### How can Lift = Weight; if airliners fly with Thrust-to-Weight ratios = 0.3? [closed]

Question: I'd appreciate it a lot if anyone could explain how the wings can generate lift that is 3.3x more than engine thrust? Is there any experimental proof that this? Or is the assumption that ...
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### Lift => Mass, for a helicopter in a hover; not Lift = Weight? [closed]

Background: According to Newtonian mechanics, a helicopter in a stable hover accelerates ('a') a mass of air ('m') downwards to generate a downward force; according to Newtons 2nd law (Force = ma). ...
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### Effiency during submarine gliding

Imagine a sort of submarine glider using gravity downwards and buoyancy upwards. An air pump is needed to press air into pressure vessels when ballast tank is filled with water, but I guess that's all....
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### What direction of aerodynamic force does the cylinder experience?

What direction of aerodynamic force does the cylinder experience? Spray gas from nozzles A and B respectively in the tangent direction of the cylinder. The air from a is faster than the air from B. I ...
33 views

### Why does the air at the top of the wing move down?

Why does the air at the top of the wing move down? I think it's because of a negative pressure field. Some people think it's the viscosity of the fluid. Why does the air at the bottom of the wing move ...
143 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 ...
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### Lift of an airfoil: viscous vs inviscid results

I am trying to understand the difference between the lift computed with an inviscid solver (Euler equations) and the one computed with a viscous solver(Navier Stokes equations). At this point, I ...
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### Will the ejected fluid create low pressure on the upper surface of the wing?

As shown in the figure, A is the wing, B is the nozzle, and C is the fluid ejected from the nozzle. Q: is there a low pressure on the upper surface of the wing when the fluid is ejected from the ...
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### Earth magnetic field space elevator. No cable [closed]

I have an idea that the space elevator can be build in the following conditions: Not a classic theory. No cable. No Geostatic orbit. Not equator platform position The possible platform / base ...
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### If the wing is absolutely smooth and has no friction, will it still generate lift?

I think it will generate lift, because downwash air flow still exists. But I'm not sure if I'm right.
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### 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 ...
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### Why is the top of the wing low pressure?

I think it's because the wing has an angle of attack and the flow passage at the top of the wing is widened, so the resistance of air flow at the top of the wing is reduced. But some people don't ...
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### Is Upside-down Racing Possible?

Based on the calculations I have done, upside-down racing seems to be possible. But in my mind, and certainly others too, it seems outlandish and impossible. Here is what I have come up with, please ...
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### Can I explain lift in this way?

** As shown above, Suppose the wing moves horizontally.** The red arrow is the direction of air movement at the top of the wing. This direction is not perpendicular to the normal line at the top of ...
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### (Lifting of aircraft wings) Source of centripetal force on a curved streamline?

I am trying to understand how wings lifting work in airplanes. One explanation is found here Basically a fluid portion on curved streamline will experience a centripetal force. This centripetal ...
135 views

### Why doesn't my flight aerodynamics maths work? [closed]

Context: For some context, I'm a game developer and I'm building a flight sim game. My goal is to have realistic flight physics -- not arcade physics. I'm having issues with the maths -- it is not ...
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### Vacuum balloon / airship with balloons as shell segments

What are the problems with the following idea for building a vacuum balloon / airship? The question is targeted at the "making it float" part, ignoring other problems with super-light airships (...
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### Generating lift by Naruto running

"Naruto running" is running with your arms behind you (pictured above). Many characters in the Naruto series are superhuman and can run way faster than a normal human. I thought that they run like ...
176 views

### This is my bucket experiment. I use this experiment to explain lift. Am I right?

Hang the bucket on a long rope. Rotate the bucket to tighten the rope. Then fill the bucket with water and close the lid (shown in the blue line). At this time, the bucket and water are in a static ...
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### Do drones fly because of low pressure above them or high pressure below them?

I was working on some drone battery life solutions and was stuck with the question whether drones fly because of low pressure created above them by the rotor or due to high pressure created below them....
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### The physics of airplane flight [closed]

Physics in schools teaches two contradictory and mutually exclusive things: (1) That the upward lift force on an airplane in flight equal its weight (Lift = Weight = mass x gravity). This is based on ...
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### Pressure and upthrust force

What is upthrust force? Is is the pressure difference or just pressure x Area at the bottom of the surface? How does upthrust force change with depth in liquid?
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### Angle of attack and lift: is there a model?

The relation between the angle of attack $\alpha$ of an airplane's wing and the lift $F$ generated by it is quite complex. If I treat air particles as tennis balls hitting the wing at the front, then ...
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### What is the lift coefficient of human body?

Assuming we can change angle of attack by changing our hands orientation what is the maximum aerodynamic lift coefficient of human body?
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### At what wind speed will a ceiling fan 10 feet above my desk move a sheet of paper? [closed]

We sell fans. An engineer asked this question. He wants to buy a fan large enough to cool without being so large it blows paperwork off his desk. Q: At what wind speed will a ceiling fan 10 feet ...
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### Is it possible to substitute wind speed for the speed of an aircraft in the lift equation $L = \frac12 dv^2sCL$

As in, how would you calculate the amount of lift an aircraft experiences, if for example the plane itself was stationary in a wind tunnel but is subject to high wind speeds and as a result ...
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### Would a puddle of spill milk on the elevator floor float when I cut the cable?

Imagine I pour some milk inside the elevator and then I cut the cable to allow the elevator to free fall, does it immediately float or only when the elevator speed has reached 9.81m/s/s? Oh and assume ...
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### Please explain airflows above and below aerofoils for a layman

I have read about the lift of airfoils a lot recently and just want a few things cleared up. When incoming airflow hits a typical cambered airfoil and diverges into “top” and “bottom” air flows, why ...
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### Is Bernoulli's equation the correct explanation of a curved soccer ball? [duplicate]

I saw a lot of materials supposing that the Bernoulli's equation explains the curvature of a soccer ball: since the ball is spinning, two sides of the ball would experience different velocities, and ...
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### Drag of flat plate at any orientation in 3D

I am trying to calculate the force vector on a flat plate caused by wind, when that plate is not perpendicular to the wind. Imagine a sailboat, and assume that its sail is a rectangular flat plate. ...
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### Thrust needed from an engine to reach orbit

Assume you had an airplane with magical engines that didn't need fuel, air or power, to operate. What thrust to ground weight ratio would the airplane need to reach orbit? By ground weight I mean mass ...
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### Why did this table tennis ball rise to the sky? [duplicate]

The nozzle makes the water flow through the upper part of the table tennis ball. If the angle and velocity of the water jet are well controlled, the table tennis ball will rise to the sky. The string ...
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### Does the weight on a car's wheels decrease with increasing speeds? [duplicate]

Ignoring the reduction in fuel weight as it burns, does the weight on a car's wheels decrease with increasing speeds? If so, by how much and is there a fomula for calculating that? At what speeds ...
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### Confusion with the $\lambda$ in this experiment

I am still having trouble seeing why on this manual for experiment ideas, that they say the $\lambda$ is constant. My question is, how do we find this value of lambda or why can it be kept constant? ...
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### Inverted flight [duplicate]

I've read the answers provided but I'm still confused that if an aerofoil is designed so that air flows faster over the upper surface for the purpose of providing lower pressure and hence lift why in ...
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### But how exactly do you calculate the Joukowsky Airfoil, within a minimal margin of error?

After reading a fair bit of theory around the uses of conformal mapping to solve for the forces of lift acting on a wing, or a 2D cross section of the wing, in relation to the angle of attack. However ...
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### How to obtain the $dC_d/dC_l^2$ value from the drag polar of an airfoil? [closed]

I'm currently trying to do an initial design for a propeller. In order to do this I'm trying to use Xrotor. Xrotor allows the user to enter certain information about both the propeller geometry, ...
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### A drone, or any lifting vehicle, enclosed in a container. Will it lift along with the container? [duplicate]

Consider a drone, or any lifting vehicle, enclosed in a container. Will it lift along with the container? Suppose I place a small drone in a large container of negligible weight and place them in ...
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### Is lift force proportional to size?

I'm trying to calculate lift force of a particular object I'm working with. However, I can't find much information on how much force is required for an object to stay in flight though. My questions ...
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### Principle of Lifting of an Aircraft [duplicate]

While using the Bernoulli's equation to deduce the upthrust on an aircraft , a statement is always made that The air particles going above th wing have to cover a greater distance in same time than ...
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### Would it generate a lift if wind is circulating inside a nearly closed tube?

For a setup like the below image, would there be a lift generated to the tube, due to bernoulli effect?
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### How fast do the aerodynamic forces on a surface build up?

I`m currently working on my thesis in the field of active car aerodynamics. In order to design a controller to move parts of the cars body I need to know how fast the drag and downforce acting on this ...
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### How do frogs and fish rain? [closed]

I saw a documentary about the rain of frogs and fish in certain areas due to water sprouts sucking them up and causing rain of frogs and fish (pretty large ones) hundreds of miles away. But how is it ...
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### Energy consumption from acceleration

I have an interesting problem. I have a machine which has to lift 35 kg (this is the total mass of the object and the lifting arm). The lifting is done by a servo motor. Now I want to calculate the ...
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### Why is the polar diagram of an airplane depended on weight?

Can anybody answer this question? Although aviation-related, it is in fact a fluid mechanics problem: https://aviation.stackexchange.com/questions/54192/why-is-polar-curve-of-a-glider-dependent-on-...
361 views

### Effect of tailwind on aircraft speed

I have been spending some time in analyzing the impact of tailwind on the ground speed of the aircraft. My analysis is based around the following equation : VAW = VAG - VWG ; where VAW is the velocity ...