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)?

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

   Tidal arrows from the Moon and the Sun. Which raises bigger tides on Earth, the Moon or the Sun, by Bo's reading (NOAA)?

   • They are exactly equal
   • The Moon; the Sun's tidal force is about half
   • Neither; Earth's spin alone makes tides
   • The Sun, since it is more massive
3. 3.

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

   • The Moon is far closer, and tidal force drops fast with distance
   • The Sun is too hot to pull on water
   • The Moon is more massive than the Sun
   • The Sun pulls on land but not water
4. 4.

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

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

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

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

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 March and April, as the spring season brings warmer seas
   • At new and full Moon, when the Sun, Moon and Earth line up
   • In the spring season
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
   • In winter
   • When the Moon is closest to Earth and pulls the hardest on the sea
   • At new and full Moon
9. 8.

   How many sets of spring tides come in each lunar month, by Ren's reading (NOAA)?

   • Twelve, one a month through the year
   • Two
   • Four
   • One, in the spring
10. 9.

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

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

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

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