Read the Following Selection
Read the following selection, or click on the play button below to listen aloud.
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.
Now, show what you know!
Complete some questions about the reading selection by clicking “Begin Questions” below.
0 of 5 questions completed
You have already completed this activity. You cannot start it again.
Activity is loading…
You must sign in or sign up to take this activity.
You must first complete the following:
0 of 5 questions answered correctly
Time has elapsed.
You have reached 0 of 0 point(s), (0)
Score: of ()
0 Essay(s) Pending (Possible Point(s): 0)
1. What two forces overcome gravity and drag so a plane can fly?CorrectIncorrect
2. What happens to the forces when an airplane is flying level and straight?CorrectIncorrect
3. One meaning of the word efficient is to use a product with the least waste or effort.
What do you think the phrase “fuel-efficient” means?
Great answer!Great answer!
Type your response above.
4. Why are jet engines important for modern planes?CorrectIncorrect
5. Fill in the blank using information from the text.
Lift is created by the differences in below the wings of a plane and above the wings.