How We Learned About Motion: teacher key

Pushes and Pulls, grade 7 edition, written for 7th grade. For nearly 2,000 years people thought objects tend to come to rest. Follow Aristotle, Galileo and Newton, and see how ramps, books and magnets changed that idea.

Read the book. Print this page for the key.

Questions and answers

1. What did people think for nearly 2,000 years before Newton?
   • That heavy things fall faster
   • That the natural tendency of objects is to come to rest (answer)
   • That moving things never stop
2. Galileo rolled a ball down one slope and up a facing slope. What did he reason about the small difference in height?
   • It came from friction (answer)
   • It came from magnets
   • It came from the ball's color
3. Why does a book sliding on a table stop?
   • It runs out of motion
   • Gravity switches off
   • Friction acts on it (answer)
4. On Earth, how is weight found?
   • Mass times g (answer)
   • Mass plus g
   • Mass divided by g
5. Why is there no drag when there is no fluid?
   • Drag needs a magnet
   • Drag comes from an object moving through a fluid (answer)
   • Drag only works on heavy things
6. What does deflects mean in the page about wings?
   • Pulls closer
   • Pushes aside (answer)
   • Heats up

Words

• inertia: resisting change
• elliptical: oval
• fluid: air or water
• poles: magnet ends
• deflects: pushes aside