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

   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)?

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

5. Read this first

   Use this

   Moon-phase calendar for one month.

6. 5.

   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
   • In the spring season
   • At new and full Moon, when the Sun, Moon and Earth line up
7. 6.

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

   • When the Moon is closest to Earth and pulls the hardest on the sea
   • In winter
   • At new and full Moon
   • At first and third quarter, with the Sun and Moon at right angles
8. 7.

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

   • One, in the spring
   • Two
   • Twelve, one a month through the year
   • Four
9. 8.

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

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

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

    • 12 hours
    • 24 hours 50 minutes
    • 29.5 days
    • 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)?

    • 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
    • The Moon spins backward