Why the tides rise and fall

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Orbit diagram of Sun, Earth and Moon with the ocean bulges drawn. What mainly causes Earth's ocean tides, by Ari's reading (NOAA)?

   • The Sun's heat warming the water
   • Wind blowing water ashore
   • The Sun's gravity alone
   • The Moon's gravity, with help from the Sun's
2. 2.

   Why does the Moon raise bigger tides than the far more massive Sun, by Kira's reading (NOAA)?

   • The Sun is too hot to pull on water
   • The Sun pulls on land but not water
   • The Moon is far closer, and tidal force drops fast with distance
   • The Moon is more massive than the Sun
3. 3.

   Earth with ocean bulges drawn, the Moon to one side. How many tidal bulges does the Moon raise on Earth's oceans, by Jun's reading (NOAA)?

   • One, facing the Moon
   • Two: one facing the Moon, one opposite
   • Four
   • One, on the far side
4. 4.

   What forms the bulge on the side of Earth away from the Moon, by Luz's reading (NOAA)?

   • The Moon pulls hardest on that side
   • Inertia beats the Moon's weaker pull there
   • The Sun's gravity pushes that water outward from Earth
   • There is no far-side bulge
5. 5.

   Earth turning through two ocean bulges. Most coasts get how many high tides each day, by Milo's reading (NOAA)?

   • Four
   • One
   • Zero; there is just one low tide
   • Two

6. Read this first

   Use this

   Moon-phase calendar for one month.

7. 6.

   When do spring tides happen, by Noah's reading (NOAA)?

   • At first and third quarter
   • In the spring season
   • In March and April, as the spring season brings warmer seas
   • At new and full Moon, when the Sun, Moon and Earth line up
8. 7.

   When do neap tides happen, by Pia's reading (NOAA)?

   • At first and third quarter, with the Sun and Moon at right angles
   • When the Moon is closest to Earth and pulls the hardest on the sea
   • At new and full Moon
   • In winter
9. 8.

   About how far apart are the two high tides on most coasts, by Tala's reading (NOAA)?

   • Exactly 24 hours
   • 6 hours 12.5 minutes
   • 12 hours 25 minutes
   • Exactly 12 hours
10. 9.

    Clock face with a lunar day marked. How long is a lunar day, by Zee's reading (NOAA)?

    • 29.5 days
    • Exactly 24 hours, the same as a solar day
    • 24 hours 50 minutes
    • 12 hours
11. 10.

    Why is a lunar day longer than 24 hours, by Esme's reading (NOAA)?

    • The Moon moves along its orbit, so Earth turns extra to catch up
    • It is not; tides repeat each 24 hours
    • The Moon spins backward
    • Earth spins more slowly at night, so each day stretches out longer