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Topic – How Does That Fly?

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How Does That Fly

What Forces Affect Airplanes?

Airplanes fly because of four forces. These forces are weight, lift, thrust, and drag.

• Weight is the force of gravity on the plane. Gravity wants to pull the plane down toward Earth.

• Lift is the force that acts to keep the plane up. Lift is created by the differences in air pressure below the wings of a plane and above the wings.

• Thrust is the force that moves the plane forward. Engines of a plane produce thrust.

• Drag is the force that wants to pull the plane backward. Drag is caused by friction between the body of the plane and the air.

For an airplane to take off, the thrust must be greater than the drag, and the lift must be greater than the weight. For an airplane to land, the thrust must be less than the drag, and the lift must be less than the weight. When the airplane is flying straight and at an even level, thrust and drag are equal, and lift and weight are equal.

Bigger and Bigger Planes

Since the first flight in a powered, controlled airplane in 1903, planes have gotten bigger and bigger. The airplane that first made air travel popular and profitable was the Douglas DC-3. Introduced in 1936, this plane could carry 21 passengers and fly 2405 kilometres non-stop. Today, the Airbus A380 can carry 525 passengers and fly 15 700 kilometres non-stop. Why can planes get so much bigger and still fly?

Bigger planes need engines that produce more speed. The invention of the jet engine allowed planes to fly faster and higher. Commercial jet planes started flying in the 1950s. Through the years, jet engines have become more powerful so planes can fly faster. They have also become more fuel-efficient. The faster a plane can fly, the more lift it will have. But weight is still important, especially when the planes are bigger and they carry more passengers. Airplane makers have done many things to keep their planes as light as possible. The bodies of airplanes are being made of materials that are lighter and yet strong. Even seats are being made of lighter materials.

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