Lift (force) facts for kids

Forces on an aircraft wing

Lift is a powerful force that pushes things up or sideways. It usually works against the pull of gravity or the direction of air or water flow. It's what helps airplanes fly, helicopters hover, and sailboats glide across the water.

What is Lift?

Lift is one of the four main forces that act on an aircraft, along with weight, thrust, and drag. Think of it as the upward push that lets a plane leave the ground. But lift isn't just about going up! It can also push things sideways, like a sail on a boat. It can even push things downwards, like the special wing on a race car that helps it stick to the track.

How Does Lift Work?

The simplest way to understand lift, especially for an airplane wing, is to think about how it pushes air. When a wing moves through the air, its shape causes the air to be pushed downwards. According to Newton's Third Law (which says that for every action, there's an equal and opposite reaction), if the wing pushes the air down, the air pushes the wing up. This upward push is the lift force.

Where Do We See Lift?

You can find lift in many places, not just on airplanes!

• Aircraft: The wings of airplanes create lift to fly.
• Helicopters: Their spinning rotors act like wings to lift them into the air.
• Boats: Propellers on boats use lift to push water backward, moving the boat forward.
• Sailboats: Sails use the wind to create lift, pushing the boat sideways through the water.
• Wind Turbines: The blades of a wind turbine are shaped like wings. The wind creates lift on these blades, making them spin and generate electricity.
• Fans: The blades of a fan create lift to push air around a room.

Images for kids

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  The 1902 Wright Glider shows its lift by pulling up

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  A cross-section of a wing defines an airfoil shape.

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  Angle of attack of an airfoil

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  An airfoil with camber compared to a symmetrical airfoil

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  Airflow separating from a wing at a high angle of attack

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  Flow around an airfoil: the dots move with the flow. The black dots are on time slices, which split into two – an upper and lower part – at the leading edge. A marked speed difference between the upper-and lower-surface streamlines is shown most clearly in the image animation, with the upper markers arriving at the trailing edge long before the lower ones. Colors of the dots indicate streamlines.

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  Comparison of a non-lifting flow pattern around an airfoil; and a lifting flow pattern consistent with the Kutta condition in which the flow leaves the trailing edge smoothly

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  Cross-section of an airplane wing-body combination showing the isobars of the three-dimensional lifting flow

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  Cross-section of an airplane wing-body combination showing velocity vectors of the three-dimensional lifting flow

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  Euler computation of a tip vortex rolling up from the trailed vorticity sheet

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  Planview of a wing showing the horseshoe vortex system

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  Control volumes of different shapes that have been used in analyzing the momentum balance in the 2D flow around a lifting airfoil. The airfoil is assumed to exert a downward force −L' per unit span on the air, and the proportions in which that force is manifested as momentum fluxes and pressure differences at the outer boundary are indicated for each different shape of control volume.

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  Illustration of the distribution of higher-than-ambient pressure on the ground under an airplane in subsonic flight

See also

In Spanish: Sustentación para niños