Why the tides rise and fall

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Table, Tide table for a beach (model data), with columns Tide, Time, Height (m)

   High, 5:10 a.m., 1.8; low, 11:22 a.m., 0.3; high, 5:35 p.m., 1.7; low, 11:47 p.m., 0.4.

2. 1.

   Bo reads the tide table before exploring tide pools. What is the drop from the morning high to the late-morning low?

   • 1.5 m
   • 1.8 m
   • 0.3 m
   • 2.1 m
3. 2.

   How long is it from the 5:10 a.m. high tide to the 5:35 p.m. high tide, by Jun's math?

   • 6 hours 12 minutes
   • 24 hours 50 minutes
   • 12 hours 25 minutes
   • 12 hours
4. 3.

   Tidal force ∝ mass ÷ distance³; Sun 27 million times the mass, 390 times the distance. NOAA: the Sun has 27 million times the Moon's mass but is 390 times as far away. Tidal force ∝ mass ÷ distance³. Compare the Sun's tidal force with the Moon's, by Kira's math.

   • About 27 million times stronger
   • About 177 times stronger
   • About 0.46, under half
   • About 69,000 times stronger
5. 4.

   Gravity ∝ mass ÷ distance²; Sun 27 million times the mass, 390 times the distance. Gravity ∝ mass ÷ distance². With the same numbers (27 million times the mass, 390 times as far), how does the Sun's pull on Earth compare with the Moon's, by Luz's math?

   • About 0.46 times as strong
   • About 27 million times stronger
   • About 177 times stronger
   • About 390 times stronger
6. 5.

   The Sun's pull on Earth (long) and its tidal effect (short). The Sun pulls on Earth about 177 times harder than the Moon, yet its tides are about half as big. Why, by Milo's reading (NOAA)?

   • Tides depend on distance cubed, which shrinks the Sun's effect
   • The Moon has more mass than the Sun
   • Tides follow gravity, which falls as distance squared
   • The Sun's gravity cannot reach the oceans
7. 6.

   Moon orbit diagram with perigee and apogee marked. When are tidal ranges larger than average, by Pia's reading (NOAA)?

   • When the Moon is at apogee, farthest away
   • In the spring season
   • When the Moon is at perigee, closest to Earth
   • On cloudy days
8. 7.

   Earth's orbit with perihelion marked about January 2. Earth is closest to the Sun about January 2 (NOAA). What happens to the tides then, by Ren's reading?

   • Tides become smaller
   • Tidal ranges are a little larger
   • Tides stop for the day
   • Spring tides happen in January alone
9. 8.

   At full Moon, the Sun and Moon are on opposite sides of Earth. Why is that still a spring tide, by Tala's reading?

   • Their bulges line up along one line and add together
   • Opposite sides cancel, so tides are small
   • The Sun's bulge sits across and cancels
   • Full Moonlight lifts the water
10. 9.

    At first quarter Moon, why are tides moderate (neap), by Zee's reading (NOAA)?

    • The Sun's tide is at a right angle and partly cancels the Moon's
    • The Sun and Moon line up
    • It is winter at first quarter
    • The Moon is closest then
11. 10.

    Moon-phase calendar starting at new Moon on Monday. A spring tide comes with Monday's new Moon. About when is the next spring tide, by Ari's reading?

    • About two weeks later, at full Moon
    • Next spring
    • About two months later
    • About one week later, at first quarter