Air Pushes Back: teacher key

Airplanes, grade 5 edition, written for 5th grade. How does a wing make lift? Two descriptions explain the same force. Find out how speed, thin air, flaps and engines matter, and how the Wright brothers got ready for 1903.

Read the book. Print this page for the key.

Questions and answers

1. What are the two ways to explain lift?
   • Air pressure above and below the wing, and the wing pushing air downward (answer)
   • Engine thrust and the plane's weight
   • The color of the wing and its length
2. What happens to lift when a plane flies faster?
   • It gets less
   • It stays the same
   • It grows with the square of the speed (answer)
3. Why must a plane fly faster at high altitude to keep the same lift?
   • The air gets thinner as a plane climbs (answer)
   • The wings get smaller
   • The engines get colder
4. What do flaps add to help a plane slow down for landing?
   • Lift
   • Drag (answer)
   • Thrust
5. What is a slat?
   • A movable part on the front edge of a wing (answer)
   • A kind of propeller
   • A part of the engine core
6. How long did the Wright brothers test gliders at Kitty Hawk before trying an engine?
   • Three years (answer)
   • Three days
   • Thirty years

Words

• downwash: air pushed down
• flaps: back wing parts
• slat: front wing part
• drag: air pushing back
• turbofan: engine with fan