Measuring a Push: teacher key

Pushes and Pulls, grade 6 edition, written for 6th grade. Every force has a size and a direction, and forces add up to decide what happens. Learn net force, momentum, circles and the units scientists use.

Read the book. Print this page for the key.

Questions and answers

1. In what unit do scientists measure force?
   • Kilograms
   • Newtons (answer)
   • Pounds of mass
2. What happens when the string holding a spinning ball breaks?
   • The ball stops at once
   • The ball spins faster
   • The ball flies off in a straight line (answer)
3. What is momentum?
   • A thing's mass times its velocity (answer)
   • The pull of gravity
   • The size of a push
4. Two equal forces push on a thing from opposite sides. What is the net force?
   • Twice the size of one force
   • The forces cancel out (answer)
   • Too small to measure
5. Why does a swimmer move away from the pool wall when pushing on it?
   • The wall pushes back (answer)
   • Gravity pulls the swimmer
   • Friction speeds the swimmer up
6. What does balanced mean when it is about forces?
   • Pointing the same way
   • Smaller than gravity
   • Equal and pointing in opposite directions (answer)

Words

• newtons: units of force
• centripetal: center-seeking
• momentum: mass in motion
• balanced: equal and opposite