Questions tagged [lift]

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

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1answer
189 views

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 ...
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4answers
164 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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3answers
104 views

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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4answers
213 views

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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1answer
32 views

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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1answer
41 views

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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41 views

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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32 views

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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2answers
23 views

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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2answers
33 views

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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4answers
105 views

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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28 views

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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44 views

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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63 views

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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1answer
35 views

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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56 views

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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34 views

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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1answer
38 views

How to obtain the $dC_d/dC_l^2$ value from the drag polar of an airfoil?

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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3answers
131 views

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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2answers
55 views

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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1answer
96 views

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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3answers
50 views

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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1answer
43 views

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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1answer
78 views

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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1answer
128 views

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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1answer
77 views

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-...
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201 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 ...
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4answers
655 views

What causes the air speed difference above and below the wing of a plane?

I am studying about the lift generated by a fluid flowing on a surface. In the case of an airfoil I have seen that there are various ways to explain it, you can use for example: the third law of ...
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1answer
44 views

Aerodynamics of wet versus dry sail

I recently read in a history book that sailing ships that really needed to go fast would pour water on their sails because "wet sails capture the wind better than dry sails." Why might this be? Does ...
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3answers
369 views

How does the lift force of an airplane work? [duplicate]

At first I thought that the lift force of an airplane wing came from the buoyant force of the air. Thus we can calculate it's lift force using $$ F_b={\rho}gV$$ However, that does not seem to be ...
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1answer
268 views

Boundary Layer Physics and Bernoulli Principle

I was taught that the relative velocity of all fluid particles directly in contact with the boundary in a fluid flow is zero. In other words, that the relative velocity of fluid particles in the ...
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2answers
87 views

Flow over Airplane Wings

I recently read this from Wikipedia in an article discussing lift. A fluid flowing over the surface of a body exerts a force on it. It makes no difference whether the fluid is flowing past a ...
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1answer
39 views

Flow through pipe while being lifted from water [closed]

The setting is as follows. A hollow pipe (flooded) with radius R-pipe is being lifted from below the water surface (totally submerged) to above the water surface with a speed of v1. The pipe is closed ...
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0answers
94 views

Why the paper plate is sucked?

In the diagram below, A is a disk and C is a pipe, the A and C combination is a nozzle, B is a board. As long as B is close enough to A, with the air from the D, B will be sucked and will not fall ...
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28 views

What is a simple, effective, and physically consistent explanation of Bernoulli's principle (in the context of airfoil lift)? [duplicate]

I am not here to continue any debate about what really allows airplanes to fly. Rather, what I am looking for is an informed, thoughtful, illuminating and self-contained explanation of Bernoulli's ...
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2answers
178 views

Forces acting on a helicopter

I was wondering about the force that a helicopter produces to descend to the ground being always upwards. How does that happen? I understand that it must be upwards but can't imagine it, how do the ...
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1answer
256 views

Determining tension and free body diagrams for a three-stage linear slide

I'm trying to compute the torque and current requirements on a motor powering a three-stage linear slide. I have included a diagram of the system below: The first stage (right-most) is fixed to the ...
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2answers
94 views

Why do boats carry cargo above water?

This might be a really dumb question, but why do boats carry cargo above water? For example, I can pick up a rock under water that is too heavy to pick up on land. The water has an upward lift on ...
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1answer
101 views

What happens if a helicopter's propeller spins in reverse?

I know airplanes and helicopters fly thanks to the same principle, the Bernoulli Principle. The wings and blades are designed so that the air travels faster across the up side than it does on the ...
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2answers
417 views

Coaxial rotors and thrust

I'm only a HS physics student, so please bear with my lack of jargon. My question goes like this: In the scenario of two coaxial rotors spinning independently in two different directions, each with ...
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5answers
544 views

How does this cup-with-a-cylinder-inside puzzle work?

There is a desk-top puzzle making its way around my university, sold as "Newton's Gravity Defying Puzzle". It consists of a cup with a little cylinder that sits inside. Here are some pictures: The ...
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1answer
131 views

Why neglect gravity in Kutta-Joukowski theorem?

In an example I was asked to calculate the lift force using Bernoulli's equation $$u^2/2 \ + p/\rho +gz \ = \ constant$$ and show that its consistent with Kutta-Joukowski theorem, but seems like ...
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1answer
2k views

Why is a piece of paper lifted upward even when blown below?

According to Wikipedia, A correct explanation of why the paper rises would observe that the plume follows the curve of the paper and that a curved streamline will develop a pressure gradient ...
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0answers
81 views

How to calculate lift and drag of a non-standard aerodynamic body

It is my understanding that the standard method to calculate the lift and drag characteristics of an airfoil is to use formulae and existing data of its coefficients of lift ($C_l$) and drag ($C_d$). ...
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1answer
57 views

How many calories are burned by lifting 80 kilos once?

After some calculations i figured it was something like 192 kilocalories but it sounds a bit too much so im not sure if i did the right calculations. What i did was calculate the work and then convert ...
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0answers
52 views

What are the mathematics behind a disc being elevated by air flow?

I realize the question title is a little vague... I was at the Smithsonian air and space museum recently and they had a set-up showing a disc with an air pipe. The pipe is flowing air fairly ...
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2answers
334 views

Why does the wind speed increase when streamlines approach each other?

In my physics textbook, there's a chapter on fluids which discusses pressure, flow rate, continuity, and the Bernoulli effect. I understand why pressure gradients induce net force on a column of fluid ...
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2answers
1k views

Why does a rocket spin during launching

Why does a rocket spin during launching? https://www.youtube.com/watch?v=BuPY5l45UC8
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2answers
100 views

Lifting force applied to an object

The question is as following: Identical $K$, $L$ and $M$ containers have liquids with densities $d$, $2d$ and $3d$ respectively. A solid object with density $d$ is being dropped in all of ...