Kepler's three laws of planetary motion

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   What does Kepler's first law say about a planet's orbit, by Ari's reading (NASA)?

   • A circle with the Sun at the center
   • An ellipse with the Sun at the center
   • An ellipse, with the Sun at one focus
   • A spiral that winds toward the Sun

2. Read this first

   Orbits (NASA Planetary Fact Sheet)

   Planet	a (AU)	T (years)	e
   Mercury	0.387	0.241	0.206
   Earth	1.000	1.000	0.017
   Mars	1.524	1.881	0.094
   Jupiter	5.20	11.86	0.049

3. 2.

   Which planet in the table has the most stretched orbit, by Kira's reading?

   • Mercury, e = 0.206
   • Earth, e = 0.017
   • Jupiter, e = 0.049
   • Mars, e = 0.094
4. 3.

   two shaded slices of equal area. What does Kepler's second law say a line from the Sun to a planet does, by Jun's reading (NASA)?

   • Sweeps larger areas when far away
   • Sweeps equal areas in equal times
   • Sweeps equal distances in equal times
   • Sweeps equal angles in equal times

5. Earth's orbital speed (NASA)

   Speed	Value
   maximum	30.29 km/s
   minimum	29.29 km/s

6. 4.

   NASA gives Earth's orbital speed as 30.29 km/s at most and 29.29 km/s at least. Where is Earth when it moves at 30.29 km/s, by Milo's reading?

   • At perihelion, closest to the Sun
   • At aphelion, farthest from the Sun
   • At both points equally
   • In early July, its farthest point

7. Orbits (NASA Planetary Fact Sheet)

   Planet	a (AU)	T (years)	e
   Mercury	0.387	0.241	0.206
   Earth	1.000	1.000	0.017
   Mars	1.524	1.881	0.094
   Jupiter	5.20	11.86	0.049

8. 5.

   Which planet in the table takes longest to orbit the Sun, by Noah's reading?

   • They each take one year
   • Mercury, since it moves fastest
   • Jupiter, the farthest out
   • Mercury, the closest
9. 6.

   Mars orbits at 1.524 AU. What is its orbital period in the table, by Pia's reading?

   • 3.54 years, its distance cubed
   • 0.53 years, shorter than Earth's
   • 1.524 years, the same as its distance
   • 1.881 years
10. 7.

    Four equation cards, labeled A to D. Which equation is Kepler's third law, with T in years and a in AU, by Ren's reading?

    • T³ = a²
    • T × a = 1
    • T² = a³
    • T = a

11. Mercury (NASA)

    Point	Distance (million km)
    perihelion	46.0
    aphelion	69.8

12. 8.

    NASA lists Mercury's perihelion as 46.0 and its aphelion as 69.8 million km. By how much does its distance from the Sun change, by Tala's math?

    • 57.9 million km
    • 0 km, since its orbit is a circle
    • 23.8 million km
    • 115.8 million km

13. Earth (NASA)

    Point	Distance (million km)
    perihelion	147.1
    aphelion	152.1

14. 9.

    Earth is closest to the Sun in early January (NOAA). Why is January not summer in the Northern Hemisphere, by Zee's reading?

    • January is summer everywhere on Earth
    • The 5 million km change sets the seasons
    • Earth's orbit is a perfect circle
    • Seasons come from Earth's tilt, not its distance
15. 10.

    Earth's orbital eccentricity is 0.017 (NASA). What does that tell Esme about the shape of the orbit?

    • It is very stretched, like a comet's
    • It is stretched enough to cause the seasons
    • It is very nearly a circle
    • It is a perfect circle