Balanced and Unbalanced: teacher key

Pushes and Pulls, grade 4 edition, written for 4th grade. Forces can cancel out or change a motion. Learn about inertia, equal and opposite pushes, and why mass is not weight.

Read the book. Print this page for the key.

Questions and answers

1. What do balanced forces do?
   • Speed a thing up
   • Cancel, so the motion does not change (answer)
   • Make a thing heavier
2. A swimmer pushes on the pool wall. Why does the swimmer move away?
   • The wall pushes back (answer)
   • The water is warm
   • Gravity is a pull
3. What is mass?
   • The pull of gravity on a thing
   • How fast a thing moves
   • The amount of stuff in a thing (answer)
4. The same push is given to a heavy thing and a light thing. Which speeds up more?
   • Both the same
   • The light thing (answer)
   • The heavy thing
5. What is inertia?
   • A kind of machine
   • A pull toward Earth
   • A resisting of changes in motion (answer)

Words

• inertia: resisting change
• balanced: equal and opposite
• mass: amount of stuff
• weight: gravity pull
• friction: slowing rub