# 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.

245 questions
Filter by
Sorted by
Tagged with
42 views

### Is the pressure at the top of the wings on Mars also lower than the local atmospheric pressure on Mars?

Generally speaking, on Earth, in order to fly, the pressure on the top of aircraft wings is lower than the local atmospheric pressure. So if we fly an airplane on Mars, will the pressure on the top of ...
• 2,040
42 views

### Calculating aerodynamic forces on a random object

I've set out to designing a game that would let the user design a vehicle/plane and then fly it around and I'm interested in what would be the best way to go about the physics aspect of it. The 3d ...
• 1
60 views

### Does a helicopter fly because air is forced downwards, or because each rotor acts as an aerofoil to generate lift? [duplicate]

The answer may be a combination of the two. Does a helicopter fly because air is caught by the rotor and thrown downwards, which causes an equal reaction in the opposite direction and 'throws' the ...
• 101
35 views

### Sailboat physics

I want to program a simulation of a sailing boat, but I ran into a problem with the physical law of lift and drag $$F_D=\dfrac{C_D}{2} \rho \cdot A \cdot V^2$$ F_L=\dfrac{C_L}{2} \rho \cdot A \cdot ...
1 vote
272 views

### Explaining lift on a wing via forces

Consider the bottom of a wing. Air below the wing is deflected downwards by the wing. Hence by Newton's 3rd Law the wind must exert an equal and opposite force on the wing. Hence lift, and this makes ...
1 vote
42 views

### What will happen if 10kg massed hydrogen ballon is released in air?

Generally, a hydrogen balloon would float when released in air, but what will happen when that hydrogen balloon has a mass of 10kg. Is it the density that decides whether an object floats in air or ...
• 21
1 vote
110 views

### Newton's 3rd law, force on a rocket

Please clear up this confusion for me: I just watched the video on khan academy @7:30 where the guy explains newton's 3rd law. He explains that for a box on a table, the forces equal out so it's at ...
• 13
63 views

### Do airfoils need narrowing tails to create a forward force?

All airfoils I have seen become narrow towards the trailing edge. Is it still possible to create a forward vector force if the shape becomes wider again after a narrow middle section? I read that the ...
• 31
32 views

### Is the wing drag of induced drag + 2d drag at 0lift still accurate for cambered airfoils?

I have some work at uni that requires some aerofoil analysis to create a wing, but from the polar plots its clear that the cambered aeros have lower total 2d viscous drag (from xfoil) at the cl its ...
• 113
30 views

### Understanding lift on a rotating cylinder (inviscid)

From J.D Andersons Aerodynamics book, under the category of describing inviscid flow (over a rotating cylinder in this case), it states "...the friction between the fluid and the surface of the ...
• 113
67 views

### How can the vortex be an elemental potential flow if there is a point of curl?

Aero is not my speciality at all so apologies if missed anything. But when looking at potential flows, i thought the whole point is for there to be no rotation at any point and its that reason the ...
• 113
212 views

### How can the panel method be used to find drag and lift if it is for invicid flow?

If simple CFD softwear like XFoil and OpenVSP use the panel method to find an estimate of the drags and lifts/pressure distributions. How do they find drag and lift if the panel method works based on ...
• 113
32 views

### Why is the pressure underneath a car splitter lower than the ambient

I seem to get very mixed answers online but i don’t understand why the underside of a splitter is said to have low pressure, i get that the above pressure is higher relative, but not why the underside ...
• 113
1 vote
450 views

### Calculating upwards drift velocity of hydrogen in air, where is the error in my calculations?

I have the following problem: I'm charging a lead-acid battery in a container. The charger could fail, producing too many amperes at too many volts. Too many amperes I can easily handle in a fuse, so ...
• 123
29 views

### A rotating cylinder that is free to reorient itself, that is placed within a wind near a surface, will it prefer to orient itself in a certain way?

When there is wind at a surface, and a rotating cylinder is placed there, mounted in a way that it is free to reorient itself, can it be predicted if the cylinder will align itself in a certain way? ...
• 171
1 vote
35 views

### Forces On Toroidal Wind Tunnel wihen Wing is attached inside? [closed]

Consider the attached Toroidal wind Tunnel. The Wind tunnel is in Vacuum and the moving air and the attached wing are only inside the toroidal tunnel. Will the mounted wing on the walls of the tunnel ...
• 21
192 views

### Lift and drag forces in parachuting

EDIT: guys, I am not a physicist and it is not my study field, So even if you see my question is silly to be answered, I hope you can give me a clue. I hope you are doing well. I have some questions, ...
33 views

### How can you tell that the aerofoil has an asymmetric section only by looking at Lift to drag ratio against AOA?

I am new to aeronautics and I am interested to know how can the section of an aerofoil be determined just by looking at its lift-to-drag ratio against angle of attack ( $C_l/C_d$ as a function of AOA)....
• 21
1 vote
224 views

### How does the newton's third law generate enough lift to make the airplanes fly? [closed]

How does the newton's 3rd law generate enough reaction so as to make the airplanes fly to great heights? The airplanes push air downwards but really is that enough to make the airplanes fly to great ...
685 views

### Why does blocking a fan speed it up?

Blocking a fan makes the blades speed up. This is easiest to observe with a vacuum cleaner: the motor increases in pitch when the nozzle gets occluded. Why does making it harder to pump the air ...
• 6,531
3k views

### Is it possible to statically generate lift with the difference in pressure like wings?

If I understood it correctly, the shape of the wings and/or propellers generates lift/thrust with the difference in pressure in both sides of the wings/propellers; where the lower side has higher ...
• 277
56 views

### How can an airfoil create more lift than drag?

According to law of conservation of energy, energy can only be converted, not created. Airfoils convert airspeed to lift, or to put it differently, they create a positive lift force by creating a ...
• 131
1 vote
76 views

### Why can't I pump something full of electrons and use it as a hoverboard?

Why can't I pump something full of electrons and use it as a hoverboard? I'm not sure how to calculate how many electrons a material can hold.
1 vote
30 views

### How does torque frequency affect a wing's movement? [closed]

Preface I'm playing with a python based simulation in which I solve the ODE $I\ddot\phi=\tau_{motor}-\tau_{drag}$. This ODE represents Newton's 2nd law (in terms of torques) of a wing that is attached ...
97 views

71 views

### Where can I find the theory of lift? [closed]

Website, paper, book, anything that contains the whole theory.
148 views

### Why a simple theory of lift like the one described below, is not accepted? [closed]

Why a simple theory of lift like the one described below, is not accepted? If you don’t agree with the following, please just skip this question and do not delete or downvote it, because it is a ...
44 views

### What are the methods to measure drag caused by an airfoil in a common high school labatory?

I am currently planning to do an investigation on aircraft flaps. I am trying to find a correlation between the angle of the flaps setting and the lift-drag ratio (coefficient of lift over the ...
128 views

### Where is energy for work performed by unpowered objects coming from?

Let's consider two simple effects for which equivalent everyday examples are easy to find: A helium balloon lifts a piece of rock from the ground into the air. A permanent magnet lifts a nail off ...
• 129
16 views

### Can ultrasounds generate lift?

Imagine a plate, the bottom side is flat and the top has dimples (or other structures that increase surface area) If we vibrate it ultrasonically left and right wouldn’t it experience lift because of ...
• 119
341 views

### How to calculate the energy and power of the force of lift that acts on a cruising plane?

Say we have a plane flying at constant speed and altitude. Looking at the y axis, the lift cancels out the force of gravity as it maintains constant height. I want to calculate the energy used to ...
1 vote
690 views

### 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 ...
• 11
9k views

### 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 ...
• 2,137
584 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
2k views

### 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 ...
• 13
1 vote
236 views

### 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 ...
• 11
76 views

### 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
525 views

### 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 ...
107 views

### 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 ...
• 2,040
78 views

### 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 ...
• 277
134 views

### 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.
• 2,040
1 vote
113 views

### 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?
275 views

### 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, ...
• 2,714
1 vote
75 views

### 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 ...
642 views

### 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 ...
• 121
261 views

### 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 ...
1 vote
130 views

### 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 ...
104 views

### 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 ...
• 2,040