How do airplanes fly?

What is the downward force that acts on an airplane in flight?

• lift

• drag

• thrust

• gravity

As an airplane moves forward, the shape of its wings causes a difference in pressure below and above the wings. What is the effect of this difference in pressure?

• a downward force is created

• the airplane speeds up

• an upward force is created

• the airplane slows down

“As an airplane’s propellers spin, they give the airplane a forward force (thrust). […] As an airplane moves forward, the shape of its wing creates lower pressure above the wing than below, yielding a net upward force known as lift.” Based on this evidence, what conclusion can be drawn about thrust and lift?

• Airplanes do not need lift to fly, as long as they have thrust.

• Airplanes need lift in order to create thrust.

• Airplanes can create lift without any thrust.

• Airplanes need thrust in order to create lift

Which of the following would probably help an airplane to take off and remain in flight?

• having a large body and small wings

• moving at a slow speed while on the ground

• being made from a lightweight material

• carrying heavy luggage inside the plane

What is the main idea of this text?

• Airplanes fly as a result of the forward force of thrust being greater than the backward force of drag.

• The upward force called lift is caused by a difference in air pressure above and below an airplane’s wings.

• Four different forces called thrust, drag, lift, and gravity, all prevent airplanes from being able to fly.

• Airplanes fly as a result of the upward force of lift being greater than the downward force of gravity.

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Why might the author have chosen to include three diagrams in this text?

• to illustrate the forces being discussed

• to introduce new information into the text

• to give examples of how different planes fly

• to provide an alternate explanation of how planes fly

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Choose the answer that best completes the sentence below: As an airplane speeds along the runway, the airplane’s wings disrupt the flow of the air. ____, the air above the wings moves faster than below the wings.

• However

• As a result

• For instance

• Previously

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