Why Things Stop: teacher key

Pushes and Pulls, grade 2 edition, written for 2nd grade. A ball rolls and then it stops. Find out how friction and drag slow things, and how every push gets a push back.

Read the book. Print this page for the key.

Questions and answers

1. What is the force called when air or water slows a moving thing?
   • Gravity
   • Drag (answer)
   • Friction
2. What does friction do?
   • Slows things that slide (answer)
   • Speeds things up
   • Pulls things down
3. A fish pushes water backward. Which way does the water push the fish?
   • Backward
   • Up
   • Forward (answer)
4. A thing sitting still will stay still until what happens?
   • It gets tired
   • A push or a pull moves it (answer)
   • The sun comes up
5. A thing moves through water. What will the water do to it?
   • Slow it down (answer)
   • Speed it up
   • Turn it into air

Words

• force: push or pull
• friction: slowing rub
• drag: air slowing things
• gravity: pull toward Earth