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

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

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?

   • Mars, e = 0.094
   • Mercury, e = 0.206
   • Jupiter, e = 0.049
   • Earth, e = 0.017
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 larger areas when far away
   • Sweeps equal angles in equal times
   • Sweeps equal distances in equal times
   • Sweeps equal areas 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
   • At the same speed everywhere
   • Halfway between the two
   • 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.

    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
11. 8.

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

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

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
    • Earth's orbit is a perfect circle
    • The 5 million km change sets the seasons
    • 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 very stretched, like a comet's
    • It is a perfect circle
    • It is very nearly a circle
    • It is stretched enough to cause the seasons