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)?

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

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

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?

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

   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 equal areas in equal times
   • Sweeps larger areas when far away
   • Sweeps equal distances in equal times
   • Sweeps equal angles in equal times
6. 5.

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

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

7. Earth's orbital speed (NASA)

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

8. 6.

   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 perihelion, closest to the Sun
   • At aphelion, farthest from the Sun
   • At both points equally

9. 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

10. 7.

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

    • 1.881 years
    • 0.53 years, shorter than Earth's
    • 1.524 years, the same as its distance
    • 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?

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

12. Earth (NASA)

    Point	Distance (million km)
    perihelion	147.1
    aphelion	152.1

13. 9.

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

    • Seasons come from Earth's tilt, not its distance
    • The 5 million km change sets the seasons
    • Earth's orbit is a perfect circle
    • January is summer everywhere on Earth
14. 10.

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

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