Why the Tower Sways: teacher key

How Buildings Stand Up, grade 9 edition, written for 9th grade. Tall buildings are shaped by wind and by argument. Follow the fight over the first skyscraper, the physics of swirling wind, Khan's tubes and the damper that steadies a New York tower.

Read the book. Print this page for the key.

Questions and answers

1. What can the changing, gusty part of wind pressure do to a tall building?
   • Make it sway (answer)
   • Make it shorter
   • Make it warmer
2. Why is the title of first skyscraper argued?
   • Nobody knows the year
   • Earlier buildings such as Oriel Chambers already had iron frames (answer)
   • It was never built
3. Which buildings sway more?
   • Short, wide ones
   • Ones with no windows
   • Tall, thin ones (answer)
4. Why do designers round corners and taper tops?
   • Sharp corners get uneven wind pressure that can twist a building (answer)
   • It saves steel
   • Round corners are easier to paint
5. Which two things are the dominant considerations in designing tall buildings?
   • Wind and gravity (answer)
   • Color and price
   • Snow and sound

Words

• cantilever: fixed-end beam
• vortices: air swirls
• masonry: brick or stone
• outriggers: core-to-wall arms