How Engineers Know: teacher key

Airplanes, grade 9 edition, written for 9th grade. Wind tunnels, models and a lift coefficient let engineers predict how a wing will fly before it does. Follow the forces, the Wrights' borrowed science, and the first jet airliners.

Read the book. Print this page for the key.

Questions and answers

1. What is lift, compared with drag?
   • The part of the aerodynamic force at right angles to the flow, while drag is along the flow (answer)
   • The part along the flow, while drag is at right angles
   • The same thing as weight
2. About which point does an airplane rotate?
   • Its center of gravity (answer)
   • Its nose
   • Its left wing
3. What does the lift coefficient let engineers do?
   • Predict lift at other speeds, altitudes and wing areas (answer)
   • Measure fuel in the tanks
   • Count the passengers
4. Why do some wind tunnels hold models with magnetic fields?
   • So there are no stands to disturb the airflow (answer)
   • To make the model glow
   • To make the fan louder
5. When did the Wrights become famous?
   • December 17, 1903
   • August 8, 1908 (answer)
   • In 1889
6. What did the Boeing 307 Stratoliner become the first of?
   • Pressurized airliner (answer)
   • Jet airliner
   • Supersonic airliner

Words

• vortices: swirls of air
• downwash: air pushed down
• coefficient: a measured number
• turbofan: engine with fan