Gravity — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. If a ball takes 2 seconds to fall to the ground, the round trip up and back takes about 4 seconds.
By symmetry, time up equals time down, so total is 2 + 2 = 4 seconds.
2. A pendulum swings because gravity always pulls the bob back toward the lowest point.
Gravity gives the bob a restoring force toward its lowest position.
3. If gravity pulls down with 9.8 m/s squared, after 1 second a free-falling object moves about 9.8 m/s.
Speed = acceleration x time = 9.8 x 1 = 9.8 m/s.
4. After 2 seconds, the same free-falling object reaches a speed of about 19.6 m/s.
9.8 x 2 = 19.6 m/s downward.
5. A pendulum bob is heaviest at the bottom of its swing because gravity has done positive work.
Gravity moves the bob downward, doing positive work that increases speed.
6. A satellite orbits because Earth gravity pulls it inward toward the planet.
Gravity pulls satellites inward toward Earth, balancing their forward motion in orbit for Grade 5.
7. On the Moon, you would weigh about 1/6 as much as on Earth (one-sixth).
Moon gravity pulls about one-sixth as strong, so weight is one-sixth of Earth weight for Grade 5.
8. A pendulum swings back and forth because of gravity pulling it down at each end.
Gravity pulls the pendulum bob back toward its lowest point, causing the swing for Grade 5.
9. When you jump, you come back down because gravity pulls you toward Earth.
Gravity pulls everyone back to the ground after jumping, regardless of how high we go for Grade 5.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Pendulum bob at top
→ Highest point with zero speed
Slowing down due to gravity
Pendulum bob at bottom
→ Maximum speed in the swing
Maximum speed in the swing
Ball going up
→ Slowing down due to gravity
Speeding up due to gravity
Ball coming down
→ Speeding up due to gravity
Highest point with zero speed
At top of swing speed is zero, at bottom it is max, ball going up slows, ball coming down speeds up.