Gravity Reaches Into Space: teacher key

Gravity, grade 4 edition, written for 4th grade. Gravity holds you to the ground and keeps the Moon and planets on their paths. See how astronauts float and how people came to understand the pull.

Read the book. Print this page for the key.

Questions and answers

1. Why do astronauts on the space station float?
   • They are far from gravity
   • They and the station are falling together around Earth (answer)
   • The station is empty
2. When was Newton's theory of universal gravitation published?
   • 1687 (answer)
   • 1787
   • 1587
3. What is the main cause of tides?
   • The Sun's heat
   • The wind
   • The Moon's pull (answer)
4. What can gravity do?
   • Only push
   • Only pull (answer)
   • Both
5. What would happen to your weight on a planet with less mass than Earth?
   • You would weigh more
   • You would weigh the same
   • You would weigh less (answer)

Words

• gravity: a pulling force
• orbit: a path around
• tides: sea rising, falling
• mass: amount of stuff
• weight: pull on you