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 spiral that winds toward the Sun
   • An ellipse with the Sun at the center
   • An ellipse, with the Sun at one focus
   • A circle with the Sun at the center
2. 2.

   The orbit diagram marks point A (the ellipse's center), B (a focus) and C (a point on the curve). Where is the Sun, by Bo's reading?

   • Outside the ellipse
   • B, a focus
   • A, the center
   • C, on the orbit

3. 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

4. 3.

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

   • Jupiter, e = 0.049
   • Mercury, e = 0.206
   • Earth, e = 0.017
   • Mars, e = 0.094
5. 4.

   Orbit diagram with perihelion and aphelion marked. Where in its orbit does a planet move fastest, by Luz's reading?

   • Halfway between the two
   • Closest to the Sun, at perihelion
   • At the same speed everywhere
   • Farthest from the Sun, at aphelion

6. Earth's orbital speed (NASA)

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

7. 5.

   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?

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

8. 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

9. 6.

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

   • Mercury, since it moves fastest
   • Mercury, the closest
   • They each take one year
   • Jupiter, the farthest out
10. 7.

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

    • 1.881 years
    • 1.524 years, the same as its distance
    • 0.53 years, shorter than Earth's
    • 3.54 years, its distance cubed
11. 8.

    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?

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

12. Mercury (NASA)

    Point	Distance (million km)
    perihelion	46.0
    aphelion	69.8

13. 9.

    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?

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

14. Earth (NASA)

    Point	Distance (million km)
    perihelion	147.1
    aphelion	152.1

15. 10.

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

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