# What is Lift: Definition and 613 Discussions

A surface lift is a means of cable transport for snow sports in which skiers and snowboarders remain on the ground as they are pulled uphill. While they were once prevalent, they have been overtaken in popularity by higher-capacity and higher-comfort aerial lifts, such as chairlifts and gondola lifts. Today, surface lifts are most often found on beginner slopes, small ski areas, and peripheral slopes. They are also often utilized to access glacier ski slopes because their supports can be anchored in glacier ice due to the lower forces and realigned due to glacier movement.
Surface lifts have some disadvantages compared to aerial lifts: they require more passenger skill and may be difficult for some beginners and children; sometimes they lack a suitable route back to the piste; the snow surface must be continuous; they can get in the way of skiable terrain; they are relatively slow in speed and have lower capacity.
Surface lifts have some advantages over aerial lifts: they can be exited before the lift reaches the top, they can often continue operating in wind conditions too strong for a chairlift; they require less maintenance and are much less expensive to install and operate.

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1. ### I don't understand how to calculate the drag coefficient

I'm confused about how to solve for the Cl. I know that the equation for lift is L = Cl * r * .5 * V^2 * A, and you need the Cl to find lift. However the equation for lift coefficient that I found is (2L)/(1/2*p*u^2*S) and you need L which is lift to solve for Cl. So i don't understand how in...
2. ### B Fluid Flow Deflection Bending Ahead of Airfoil?

Hi, I am a high school teacher in need of some help explaining fluid flow. I don't have much experience with fluids at a college level. We were reviewing lift (Bernoulli's velocity/pressure relation, deflection of air downwards, etc) and I showed them: this online simulation. One student asked...
3. ### Pendulum SHO but with extra downward acceleration of the pivot

Hey guys, Can someone help me understand how to understand this problem intuitively please? How I understand is that I need to look the acceleration relative to the lift as if it were f.e. on another planet with a different acceleration. this gives me a = g - 5. But then again if I didn't look...
4. ### I may need 29 megawatts just to lift 180 kgs with ion thruster...

So after reading a great paper from Utah university (or so) they include the following equation which should apply at least to some type of electric thrusters: P(power) = T(thrust in N)*S(specific impulse in secs)*G/(2*Efficiency) x=(1800*1000*9.8)/(2*0.3) x = 29,000,000 watts needed to lift a...
5. J

### Does induced drag theory include the Lift = Weight condition?

This is usual induced drag diagram. I have 2 questions: From Kutta–Joukowski theorem Fr is always perpendicular to effective airflow. 1. Does it mean for case without effective airflow(zero induced downward velocity), Fr is perpendicular to freestream airflow,so drag is zero? When effective...
6. ### B Lifting an Object: Work, Force, and Cosine

So, from what I remember, W=F*D*cos (θ). If I'm lifting, θ=90° and so, the cos = 0. So is the work just 0? Why? I still moved the object through a distance, which is the usual non-mathematical definition of Work.
7. ### I What is the minimum force required to lift an object?

A person stands on a scale. The scale reads his mass 60 kg . Now this human moves up his body short distance like someone tries to pick a fruit from a tree. The scale will start to increase by small forces x N in which the total read of the scale is 600+x N *. The force he exerts on the scale is...
8. ### Period of spring-mass system and a pendulum inside a lift

Based on the formulas, variable ##m , k, L,g## do not change so my answer is (a) but it is not correct. Why? Thanks
9. ### F = ma for a lift (elevator) carrying passengers

Summary:: What constitutes the 'body' when applying equation of motion? I was solving this problem: 'A woman of mass 60 kg is in a lift of mass 250 kg which is accelerating downwards at 3.2 m-2. Find the tension in the cable of the lift.' when I realized that I'm not sure what constitutes the...
10. ### 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...
11. ### Car lift using suspensions as lift points

Some car lift service centers want to lift up the car by using the suspensions. I always told them to lift by the pinch weld jack points near the tires. Are there some suspension system where the service center can lift the entire car by via the suspensions. And are there some cars which they can't?
12. ### Boat Lift Design: Building 8'x12' Platform

Building a 8' x 12' platform that will hold a small boat next to my dock. The platform needs to be able to be lowered below the surface of the water (launch boat) and lift above the water (store boat). Four pilings (one each corner) that each have an electric motor & reduction gearbox that has...
13. J

### Calculate lift from pressure distribution

v=50m/s ∆Pg= -981Pa ∆𝑝𝑑 =490Pa c=1m 𝜌 = 1,225 kg m3 𝐹3 = ∫ ∆𝑝3 ∙ 1 ∙ 𝑑𝑥 𝑐 2 0 = ∆𝑝𝑔 ∫ 2∆𝑝𝑑 𝑐 𝑥𝑑𝑥 𝑐 2 0 = 2∆𝑝𝑑 𝑐 ∙ ( 𝑥 2 2 ) c⁄2 | 0 = 2∆𝑝𝑑 𝑐 ∙ 𝑐 2 4 ∙ 2 = ∆𝑝𝑑 ∙ 𝑐 4 = 490,5 ∙ 1 4 = 122,625 N Lift per unit of span = (F1) + (F2) +F3 + F4= 490.5+245.25+122,25+122,625=981N :confused: Pressure...
14. ### Max L/D Ratio: Aircraft Drag Polar Explained

Would like help as to the method rather than the answer please. Classes haven't been very clear therefore everything is self taught. Many thanks. ' The Drag polar for an aircraft is given by: CD = 0.025 + 0.08 C^2L What is the maximum Lift to Drag ratio '
15. ### A Bernoulli, lift and cause & effect

Dear all, for a book I'm writing I'm trying to understand the generation of lift by wings on a conceptual level. Some papers I used are given at the end. I won't talk about all the misunderstandings out there concerning the generation of lift. I'm interested, also from a pedagogical level, in...
16. ### Solve Lift Fan Problems: 6hp Engine, 5 Blades, 45 Degrees

Have a 6hp engine turning a 5 bladed fan at 45 degrees. this is my lift fan. The problem is that right side is drawing air in while the left side seem to be blowing air out. The fan is 17" above the ground, and 4" below the deck and parallel to the ground running at 3200rpms. What am I doing...
17. ### How many walls can this battery-powered crane lift before recharging?

A new, innovative type of crane is battery powered. Its battery has a total energy capacity U , expressed in Joule. Determine how many walls, N of mass m , the crane can lift before the battery has 20% left and needs to be recharged. The walls need to be lifted from /h_1/ to /h_2/ a new...
18. ### Understanding the Energy Required to Lift Walls

Please help, I'm really struggling to understand how to work this... work = mass * gravity * change in height w = m*g*(h2 - h1) Total energy = Sum of potential energy + Kinetic Energy work = 1/2Kinetic Energy * Potential energy ^2 w = (1/2 * K) * U^2 m*g*(h2-h1)=(1/2*k)*U^2 rearanged =...

20. ### Music Music to Lift Your Soul: 4 Genres & Honorable Mention

Best music ever. Four genres. Classical: JS Bach “Air On A G String” in the original key -- Dusseldorf Symphony Orchestra Country: Jed Zeppelin -- Workingman’s Blues [Merle Haggard]...
21. ### Calculating Hot Air Balloon Volume & Lift

Volume of hot air ballon V=((4/3 pi R^3)/2) + (1/3 pi h (R^2 + r^2 + Rh) = 2956.24 m3 Balloon: R=9m h=15m r=1m m = 750 kg H = 5000m T = 373 K p1 = 101300 Pa p2 = 50650 Pa M(air) = 0.029 kg/mol F = mg - 7350 N
22. ### Is acceleration still equal in the presence of air resistance?

I remember being told that heavier things fall at the same rate as lighter things when everything else is equal. But this guy does a demonstration of a Xenon balloon falling faster than a Neon balloon. Why? Also an overloaded plane may not be able to fly, but it has the same aero dynamics, it...
23. ### Vertical lift question (Lift a roof from beneath with limited space)

I'm trying to figure out alternative ways to lift the roof on a pop-up camper that I'm refurbishing. There is limited space, and it needs to be lifted from beneath. I'm trying to avoid completely gutting it if possible which is what I'd have to do with a standard cable system. Any ideas? It...
24. ### Can a gyroscope lift a fulcrum (and itself), hinged to the floor?

This is a purely experimental idea which I would like some help understanding A) whether it can work and B) how best to understand the mechanics of the act. Firstly, my limited understanding of gyroscopes is that a stable gyroscope will (effectively) attempt to remain at the same angle if it is...
25. ### 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...
26. ### The mathematics behind airplane lift

Hello everyone, so for my math IA, I will be exploring the principals of flight. Does any of you know a book that explains the drag/lift and other principals of flight in a detailed mathematical way ? ( It would be also preferable for it to mention the flight characteristics of an Airbus A-320...
27. ### Propeller with bell lift distribution has best thrust/power ratio?

This source http://sustainableaviation.org/sas2017/session/prandtl-wing-maximum-efficiency/index.html claims : "Bell lift distribution can be applied to propulsion systems (no more “minimum induced loss”). We believe this results in a gain of 15.4% thrust for the same input torque/power." Bell...
28. ### Propeller blade lift distribution for best thrust/power ratio?

What is ideal lift distribution for propeller blade to get best thrust/power ratio? To do this blade must has minimum drag, because drag releted to torque,and torque x RPM= power..

...
30. ### Lift generated by a flapping wing.

Hi. I am trying to find an estimate for the lift generated by a flapping wing. For this scenario, we can assume that the wing has an AoA ranging from -45 deg to 45 deg. Also, we can ignore the lift generated by the upstroke because, for this specific wing design, a majority of the lift is...
31. ### Lift, Drag, Magnus, Bernoulli, Tennis ball fuzz, etc.

Hello, My background is not fluid mechanics. Yet, I am trying, very late in life (near retirement) to understand some things, now that I have time. I have always been confused about the qualitative descriptions about the role of dimples on golf balls and fuzz on tennis balls. Sometimes, the...
32. ### What is the relationship between force, acceleration, and mass in a lift?

Much like the previous question I've posted I was quite unsure of the the method I should take and resorted after many attempts to just trial and error which resulted in getting the correct answer of 5kg after dividing the weight of 70N by 14ms^-2 (sum of upward acceleration and gravitational...
33. ### Why is lift perpendicular to the wing?

It is said that lift on a wing always acts perpendicular to the relative wind. Why is this so? Is it because we arbitrarily choose to analyze its components with one purposely chosen to be perpendicular or is it a matter of physics that the lift component is naturally perpendicular. If so...
34. ### What is the formula for calculating the coefficient of lift for an airfoil?

A C of L curve for a particular airfoil is calculated based on what? I know AOA is a part of it but is there a formula for CL itself? For example... CL= L / rho * 1/2 * V^2 * S Which is fine. but... L = CL * rho * 1/2 * V^2 * S gets a value for CL from somewhere, right? I assume it’s...
35. ### Is Turbulence Necessary for Lift on a Wing?

For the wing of a plane, as an example, I think that the circulation around the wing due to faster flow on the top is balanced by the circulation of a vortex which is formed off of the tail. Since the greater speed on the top is necessary for the lift, would that also mean the turbulent flow...
36. ### Acceleration issue -- A 120W motor starts to lift a load of 20 kg....

Okay, here is a question I just can't solve. The 120W motor starts to lift a load of 20 kg. During which time, this load will reach a speed of 0.5 m / s, taking into account the potential energy. PS: Ignore losses in the mechanism!
37. ### What units are used in spin factor and coefficient of lift formulas?

I am trying to add the magnus effect to a golf simulator program but am getting stuck on the coefficient of lift. What are the units I should be using in these calculations? The rest of my program I use SI units. But I seam to get weird results when using them with these equations. Spin factor...
38. ### When unsuccessfully trying to lift a weight, where does my energy go to?

Let's say I am strong enough to lift a 100 kg dumbbell, but not strong enough for a 200 kg one. If I lift the 100 kg dumbbell, I suppose the chemical energy of my body tranforms into the potential energy of the lifted dumbbell. Suppose I'm trying to lift the 200 kg one. I'm pulling as hard as I...
39. ### Power To Accelerate 1000kg Elevator Cab Upward

(a) When the cab is carrying its maximum capacity, at what rate must the motor deliver energy to get the cab up to cruising speed? My shot was finding the acceleration, a=1.5/2 = 0.75m/s2 Displacement of elevator Vf2 = vi2 + 2aΔx Δx = 1.5m Force of elevator (Since it accelerates...
40. ### What is the Kutta Juokowski theory for the lift of an aerofoil?

What is kutta juokowski theory for lift of aerofoil? (As people say that pressure difference theory of lift is just for basics but main lift is generated by Kutta J, Theorem) No formulae please. If someone can explain like what happens there literally? I tried searching animation or such kind of...
41. ### Aerodynamics - why wings create lift - current vs historical discussions

My son and i were discussing aerodynamics and he brought up a paper from https://phys.org/news/2012-01-wings.html It seems that the latest discussions seem to completely discount the differential velocity of air flow as a cause of differential pressure, but point to a differential pressure...

43. ### How to Calculate the Force Required to Lift an Arm

Hi, Hope one of you might be able to help me with some calculations :) I'm trying to calculate the amount of force required to lift an arm, based on weight, distances and angles. I made a sketch to illustrate my problem. where: Lac = Length of arm Lab = Distance from "anker-point" to...
44. ### Lift and drag coefficients vs AoA graphs of a specific NACA profile

Hello, I would like to understand know how the lift coefficient ##C_L## versus AoA curve and the drag coefficient ##C_D## versus AoA curve are determined for the various tabulated NACA profiles. Are computer simulation run for the different profiles assuming a certain Reynolds' number? Or can...
45. ### Flight of a plane without lift on its wings

I don't know where to start with this as I can't visualise a diagram for it. Any help would be appreciated.
46. ### What happens to a pendulum clock in a lift when the cable breaks?

I think the answer will be either (b) or (d). If the pendulum is at its amplitude when the cable breaks, then the oscillation will stop since the pendulum is also not moving at that instant. If the pendulum is at any points except amplitude, then it will hit the ceiling since it still has...
47. ### Could an Electrostatic Lift Vehicle Transfer the Earth's Atmosphere to the Moon?

Except for railguns every space launch method we have (at least partially) built has been based on the rocket engine. But with the Earth Moon system we have an opportunity to use another method. Put a 6GeV ion beam accelerator on the Moon, and transfer 400000C of charge to the Earth. This sets...
48. ### 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...
49. ### 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...
50. ### Torque with Infinity length can lift anything?

I was always wondering if you can lift anything (no matter how heavy it is) if you just use a really long pipe. Or does torque increases in a way like ##e^x## , ##a^x## and after some point it barely increases? Also if this can be explained mathematically, I would love to see it.