What is Lift force: Definition and 48 Discussions

A fluid flowing around the surface of an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it can act in any direction at right angles to the flow.
If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a hydrodynamic force.
Dynamic lift is distinguished from other kinds of lift in fluids. Aerostatic lift or buoyancy, in which an internal fluid is lighter than the surrounding fluid, does not require movement and is used by balloons, blimps, dirigibles, boats, and submarines. Planing lift, in which only the lower portion of the body is immersed in a liquid flow, is used by motorboats, surfboards, and water-skis.

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  1. Ruda975

    I Lift Force of a Rotating Sphere in the Air

    Hello, I would like to ask one question. What is the equation for the lift force of a rotating sphere when flying through the air: m = 0.25 g v = 130 m/s angular velocity = 105 rad/s radius = 3 mm air density = 1.2292 kg/m^3 air pressure = 101200 Pa air temperature = 15 °C = 288.15 K If anyone...
  2. C

    What type of ball can bounce and travel the most?

    From what I have investigated, I know that dimples do a large part of the process of going far, and elasticity for sure is something of the main bounce thing, but things that confuse me like if the ball is empty affects both characteristics, or if the same dimples affect the bounce of the ball...
  3. C

    Fulcrum, balance point and scissor lift force

    My first question, so be kind (!) Long time since I was at school, and can only remember the basics of beams and fulcrums. In essence, that a 1kg weight 5mtrs from a fulcrum / pivot needs 5kg at 1mtr to counterbalance. But what about the beam itself? Do the two sides cancel each other out? For...
  4. A

    Solenoid Lift Force Results -- Need Data Analysis

    Good Day, I am trying to pick up small ferro (Neodynium)) magnets vertically with a solenoid. I want to know how much magnetic force the solenoid can pick up. The formula I tested and actual numbers for my solenoid are in the image below. I know that the magnetic field of a solenoid is given...
  5. F

    Application point of the lift force and pitching moment

    Hello As the angle of attack of an airfoil changes, the lift force ##L## changes both in magnitude and position (not in direction, always upward). The force location is a point called the center of pressure ##x_{cp}##. It is possible to transfer the force to any another different point along...
  6. T

    Simple question about a moving elevator cab

    Homework Statement Question from fundamental of physics, Halliday Resnick Walker In Figure below, a ##m=0.250## kg block of cheese lies on the floor of a ##M=900 kg## elevator cab that is being pulled upward by a cable through distance ##d1 =2.40 m## and then through distance ##d2 = 10.5 m##...
  7. K

    Lift and Drag force in a Wind Tunnel

    Hello guys, I am trying to calculate the lift force and drag force in a wind tunnel at my school as a part of a project that i am doing. I am varying the length of the airfoils and trying to measure the lift force and drag force. I have 3-d printed 7 airfoils. However, I am not able to find any...
  8. M

    The right reason for lift force on an aerofoil

    On the internet, I found two different explanations for lift force. In one of the explanations, bernoullis equation was applied between the stream flowing under and the stream above the aerofoil(the stream above moves faster and so less pressure than the lower). The other explanation says...
  9. A

    Uses of Lift Force for Plane Surfaces

    Hello, I'm trying to find situations in which it is important or useful to look at the force generated by a difference in pressure due to an increase in velocity of a fluid. I.e, pressure changes due to Bernoulli's equation. This should be simple by itself, but I am looking for situations that...
  10. a_c_e

    Gas Spring and Linear Actuator calculation....

    May I start by saying hello to all and that I have visited the site before, but have yet to create an account until now. With that said, I am having difficulty calculating proper numbers for a project I am designing. Mind you, it has been about seven years since I was in any physics or...
  11. AlexKud

    Force required to lift a platform (over the range of angles)

    Homework Statement Hi, this is not really an academic homework but it is something I'm trying to solve for my future project. I have a background in electrical engineering hence I'm having a hard time solving the forces problem. https://dl.dropboxusercontent.com/u/43124243/Force_problem.png...
  12. R

    Can drag force and lift force be in the same direction here:

    In the attached picture, can I say that there is a lift force in the Y-direction, and a drag force too in the same Y-direction? FL proportional to V_fx2 ? FD proportional to V_py2 ? Is this equation of motion for the Y-direction correct here: ma = − mg − FD + V(rho)g + FL The lift force is...
  13. I

    Calculating Wing Lift with a DIY Scale and Air Supply

    Hi! I have attached a small sheet of wood to a stand and then all of it to a scale. After that with a air supply I've made wind go through the "wing". Due to lift, the scale showed up a negative value. Knowing that value, is it possible to calculate the lift of the wing? Thank you
  14. P

    Lift vs Thrust Force: How Is More Lift Than Thrust Possible?

    The thrust of an airplane changes the speed of the airplane, or you can look at it as it is increasing the airspeed relative to the airplane. The airspeed across the wings is only as much as the thrust allows it to be. The airspeed across the wing is what produces thrust, and I realize how it...
  15. Y

    Discovering Lift Force in Case 2

    We all know the lift force in case 1, what about case 2 ?
  16. A

    Determining Tension & Lift Force for Helicopter & Truck

    Homework Statement A 15000-kg helicopter is lowering a 4000-kg truck by a cable of fixed length. The truck, helicopter, and cable are descending at 15.0 m/s and must be slowed to 5.00 m/s in the next 50.0 m of descent to prevent damaging the truck. Assume a constant rate of slowing. Determine...
  17. O

    Calculating lift force of a motorised hovercraft

    Hello, I need help regarding calculating the lift force for a hovercraft. I found an equations online on thrust propulsion. Equation → T= π/4 x D^2 x (v + Δv/2) x ρ x Δv D- diameter of propeller v- velocity of incoming flow Δv- additional velocity, accelerated by propeller ρ- density of air...
  18. T

    How is lift force proportional to speed up?

    i know that if i have a greater lift force, there will be a greater speed upwards, but i don't know to calculate a speed of something upwards. is this even possible to calculate? if it's not, can you give a calculation example??
  19. M

    How To Find The Drag and Lift Force?

    How can I find the drag and lift force such as below illustration? http://s4.postimage.org/sxmnflttp/dragillustration.png Below is my calculation: http://s4.postimage.org/ao75d6r0d/dragcalculation.png
  20. R

    Finding the lift force on an airplane

    Homework Statement A 2598kg airplane is diving (at constant velocity) making an angle of 10 degrees to the horizontal. Find the lift force on the plane assuming that it is normal to the velocity? I think my main problem is the fact that I'm having a bit trouble with understanding the...
  21. M

    Please help me to calculate drag force and lift force

    Homework Statement Hello guys, I am here and really need your help. In the figure below, the water flow from inlet and then out at outlet with velocity, v = 0.71 m/s. The objective is to calculate find the drag force and lift force act on fishing lure. I have done Ansys Fluent analysis but...
  22. S

    Lift force on car roof at 100km/hr

    1. What is the lift force on the roof of your car that has an area of 3.9m^2 if you are driving 100km/hr? use 1.17kg/m^3 for density of air. im not even sure where to start. have never done this.
  23. S

    What is the lift force on a car's roof at 100km/hr with an area of 3.9m^2?

    the question I am stumped on is "What is the lift force on the roof of your car that has an aera of 3.9m^2 if you are driving 100km/hr? use 1.17kg/m^3 for density of air
  24. A

    Fluid Mechanics; Lift Force on a Roof; Bernoulli's Equation

    Homework Statement I need to find the net force acting on a flat squared roof with area A while the wind is blowing outside at some velocity, v_1. Homework Equations Bernoulli's Equation: P_1+\frac{1}{2}\rho v_1^2+\rho gy_1= P_2+\frac{1}{2}\rho v_2^2+\rho gy_2 The Attempt at a...
  25. F

    Is there a more accurate way to calculate lift force in aerodynamics?

    Hi, I'm right now coursing IB (equivalent to A-levels) and one of the compulsory essays we must do is called Extended Essay. It's an essay you do on a topic you choose. I choose aerodynamics. Created a "wind tunnel" out of plastic and made it rigid with hard plastic pieces which were partially...
  26. Femme_physics

    Does lift force decrease as speed decreases?

    Or, to be more blunt, does "lift" force even exists in statics? I was rather surprised that our teacher told us that lift force is just as strong as the normal force in statics of an object against ground. It made me wonder just how strong is it. Does lift force decrease when speed decrease...
  27. M

    Fan design to improve lift force

    Homework Statement Can the addition of a second set of fan blades, below the first set and on the same axis, improve the lift force created? What is the theory associated with this phenomena? Homework Equations none, practical application in lab setting. The Attempt at a Solution...
  28. T

    Calculate Force to Lift Weight in Multi-Scissor Lifts

    Hello, I am building a scissor lift for a design project. I located a formula for calculating the amount of force required to lift a weight as given: F=(W+(Wa/2))/(tan(theta)) Where F is the amount of force required, W is the weight of the payload and the load platform, Wa is the weight of...
  29. U

    Can You Calculate Lift Force for a RC Quad Rotor Helicopter?

    Hello! I'm planning to start a project to design a RC controlled quad rotor helicopter. If it works out well I have an idea of making it autonomous. So first thing is that I want to know how to calculate the lift force from a single motor ?
  30. C

    Calculating Lift Force for Semi-Circle Moving Sideways

    What's the equation for the force of a lift. Drag formula is 1/2 ρ∆v^2 C A. And if you need the constant how would i determine the lift constant for a semi circle shape which spins sideways and has an acceleration of approximately 8.5 m/s down (should be gravity which is 9.8 ms/s). It is...
  31. B

    Lift Force Generated by a Wing

    Homework Statement A commercial airliner cruises at a speed of 284 meters per second. Each wing is 28.8 meters long and has an average width of 1.73 meters. The density of air at cruising altitude is 0.47 kilograms per cubic meter. How much lift force is generated by the wings if the air...
  32. A

    Finding Lift Force - Glider Wing

    I am working on my semester project and have come across a hitch. I am trying to find the Lift Force of my wing using the following equation FL=CL P A (v2/2) Where: FL is Lift Force CL is Coefficient of Lift (I think) P is the density of the fluid (Air) A is the Area V is Velocity...
  33. X

    Lift force and acceleration

    1. Homework Statement Suppose a 66-kg boy and a 42-kg girl use a massless rope in a tug-of-war on an icy, resistance-free surface. If the acceleration of the girl toward the boy is 3.0 m/s2, find the magnitude of the acceleration of the boy toward the girl. Homework Equations...
  34. T

    Lift Force from Lagrangian Mechanics

    I am having a lot of trouble conceptually understanding this issue in Lagrangian mechanics: I have an airfoil which is immersed in incompressible flow: it has two degrees of freedom: a rotation: alpha and a pitching (up down) motion: h. Now the lift is due to both alpha and the first derivative...
  35. M

    Calculating Lift Force for a Helicopter and Car System

    Homework Statement A 13,000-kg helicopter accelerates upward at 0.37 m/s^2 while lifting a 2000 pound car. To the nearest Newton, what is the lift force exerted by the air on the rotors? Homework Equations I thought since the problem is dealing with forces, I would use F=ma but that...
  36. A

    Solving Complex Structural Challenges - Can a 1000kg Lift Force Lift 950kg?

    hi, i have this problem that i am trying to figure out, but seems i need some help..:) ii have attached an image and an animation to clearly explain my problem. what i am trying to understand is will the green base with its 1000kg lift force be able to lift the pole with the red dot (950kg)...
  37. C

    Calculating Lift Force of Helicopter Propellers

    Homework Statement A 5400 kg helicopter accelerates upward at 2.17 m/s2. The acceleration due to gravity is 9.8 m/s2. What life force is exerted by the air on the propellers? Answer in N. Homework Equations Fnet=ma The Attempt at a Solution I am making the acceleration positive...
  38. T

    Does Balloon Lift Force Increase or Decrease with Altitude?

    As a helium balloon increases in altitude, the density of the air inside decreases. However, the density of the air surrounding it (The atmosphere) also decreases with altitude p=p0*exp(-z/z0), where z0 is the scale height of the atmosphere. So does this mean the lift force acting on the...
  39. V

    How Do You Calculate Lift Force on a Banked Airplane?

    Need some suggestions... I have a banked airplane at theta degrees, with a radius, and velocity. What is the formula for finding lift force. Fc = Fn sin theta I believe, but that's the only formula I am aware of. Thanks!, -Mike
  40. B

    Toy Airplane Flying: Lift Force vs. Reaction Force

    Hi I've got a question concerning a previous question I've done. A person is holding a toy airplane which flys in the air with a constant radius. is the lift force the same as reaction force? is it equal to the vertical component of the centripetal force and weight force of the airplane?
  41. T

    How Is Lift Force Calculated for a Helicopter?

    A 4600 kg helicopter accelerates upward at 2.0 m/s^2. What lift force is exerted by the air on the propellors? I don't know how to do it. Please help :confused:
  42. P

    Understanding Lift Force on Airplanes

    the force of lift excerted on an airplane is defined as F = Lc * D * v^2 * A where Lc is the lift coefficient, D is the air density, v velocity, and A the lift area of the wing structure. If i use SI units, the Force is expressed in Newtons. What I'm trying to grasp here, is how does this apply...
  43. P

    Pressure and lift force on a wing

    An airplane has a mass of 1.60-10^4 kg and each wing has an area of 40.0m^2. During level flight, the pressure on the lower wing surface is 7.00-10^4 Pa. Determine the LIFT FORCE on the plane. Is it sufficient to lift the plane? part is what concerns me: if it is in level flight, the net...
  44. T

    What is the lift force exerted by the air on the rotors?

    A 6520 kg helicopter accelerates upward at 0.57 m/s2 while lifting a 1190 kg car. (a) What is the lift force exerted by the air on the rotors? _________ N (b) What is the tension in the cable (ignore its mass) that connects the car to the helicopter? _____N I have no idea how to do...
  45. Clausius2

    On numerical calculation of Lift Force via Potential Flow

    Imagine: I want to compute numerically a POTENTIAL STEADY and INCOMPRESSIBLE flow over an airfoil. The set up of the problem is: \nabla^2\phi=0 \nabla\phi \cdot \overline{n}\big)_{x=surface}=0 no normal velocity component on the airfoil surface. \nabla \phi=\overline{U_\infty} as...
  46. D

    Calculate Lift Force of 4510 kg Helicopter Accelerating Upward

    A 4510 kg helicopter accelerates upward at 2.1 m/s^2. What lift force is exerted by the air on the propellers? The answer is in Newtons. If you can give me an equation, that would be great. Thanks
  47. K

    Spanwise Lift force distribution?

    Hi I wanted to get clear on this conclusion of lift distribution along the span of a wing. Graphs in texts show that for constant chord wings, Cl distribution along the span is eliptical. Conclusions: 1.Induced incidence is greater towards the tip. 2.Lift force at the root is PI/4...
  48. B

    Calculate the Lift Force of a 4655-kg Helicopter

    can someone give me the formula needed to work this problem? A 4655-kg helicopter accelerated upward at 8 m/s2. What lift force is exerted by the air on the propellers?
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