Name:
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Planetary Systems and Motion Review
Indicate whether the statement is true or false. If it is false, change the identified word(s) to make the statement
true.
1. In the early 1500s, Tycho Brahe formulated the heliocentric model of the solar system. _________________________
2. Kepler’s first law demonstrates that each planet has an elliptical orbit of unique size and shape with the Sun at one
focus. _________________________
3. Galileo’s discovery of Jupiter’s moons proved that not all celestial bodies orbit Earth; therefore, Earth is not necessarily
the center of the solar system. _________________________
Indicate whether the statement is true or false.
4. Interstellar clouds called nebulae are primarily composed of nitrogen and oxygen.
a. True
b. False
5. The force of gravity between two objects is determined entirely by their masses.
a. True
b. False
6. The inner planets have greater densities than the outer planets.
a. True
b. False
7. The shaded area of the graph shows the percentage of the total planetary matter in the solar system that is part of
Earth’s mass.
a. True
b. False
Indicate the answer choice that best completes the statement or answers the question.
8. What force draws the matter in an interstellar cloud together to form a star?
a. electric
b. gravity
c. magnetism
d. friction
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Planetary Systems and Motion Review
9. Which two planets are separated by a distance of 1.13 AU?
a. Mercury and Mars
b. Mars and Venus
c. Earth and Mercury
d. Mars and Earth
10. At which labeled interval of its orbit would the planet move with the greatest velocity?
a. A
b. B
c. C
d. D
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Planetary Systems and Motion Review
Reviewing Vocabulary
Describe the differences between each concept in one or two sentences.
11. Kepler’s laws of planetary motion, Newton’s law of universal gravitation
_________________________________________________________________________________________________
_________________________________________________________________________________________________
_________________________________________________________________________________________________
12. terrestrial planets, gas giant planets
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_________________________________________________________________________________________________
_________________________________________________________________________________________________
Thinking Critically
Planetary Motion
Kepler’s laws of planetary motion demonstrate that each planet’s orbit around the Sun sweeps out in a shape called an
ellipse, rather than a circle. This means that a planet does not maintain a constant distance from the Sun. Use the
following diagrams to label the parts of these elliptical orbits
13. Use the terms below to label the two diagrams above.
foci
major axis
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semimajor axis
farthest from Sun
closest to Sun
Sun
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Name:
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Planetary Systems and Motion Review
Match each item with the correct statement below.
a. Kepler’s second law
b. law of universal gravitation
c. Planetary nebula
d. retrograde motion
e. planetesimals
14. The movement of a planet in an opposing direction across the sky _______
15. The disk of dust and gas that formed the Sun and planets ________
16. Tiny grains of condensed material accumulate and merge together to form these large bodies that grow until they
reach hundreds of kilometers in diameter _______
17. An imaginary line between the Sun and a planet that sweeps out equal amounts of area in equal amounts of time ____
18. The statement that describes the relationship among the masses of two bodies and the force and distance between them
__________
The test will include one of these questions that will require an answer of three or more sentences, use this study guide to
formulate answers for both.
19. Explain why the term universal is included in Newton’s universal law of gravitation.
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
20. Predict how the force of gravity between the Earth and Moon would change if the Moon’s mass was suddenly greatly
decreased by the impact of an asteroid.
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
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Planetary Systems and Motion Review
Answer Key
1. False - Nicolaus Copernicus
2. True
3. True
4. False
5. False
6. True
7. False
8. b
9. a
10. a
11. Both explain planetary motion. Kepler’s laws showed that planets orbit in a shape called an ellipse. Newton’s law of
universal gravitation determined that each planet orbits a point between itself and the Sun called the center of mass.
Kepler’s laws were based on observations, while Newton’s law of universal gravitation was based on computations.
12. Both are categories of the planets of our solar system. Terrestrial planets are the four planets close to the Sun:
Mercury, Venus, Earth, and Mars. They have solid, rocky surfaces and are smaller. Gas giant planets are farther from the
Sun: Jupiter, Saturn, Uranus, and Neptune. They are more gaseous, lack a solid surface, and are larger.
13. 1. major axis
2. foci
3. semimajor axis
4. closest to Sun
5. Sun
6. farthest from Sun
14. c
15. e
16. d
17. f
18. a
19. b
20. The force of gravity acts on all objects in the universe, therefore the term universal is included in the title of Newton’s
description of the force of gravity.
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Planetary Systems and Motion Review
21. If the mass of the Moon decreased, the force of gravity between the Earth and Moon would decrease.
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