7.2.2 Kepler's Three Laws

Question 1

Kepler’s Three Laws

Answer 1

• Kepler’s first law: The path of an object in a closed orbit around the Sun is an ellipse with the Sun at one focus.
• Kepler’s second law: For an object in a closed orbit around the Sun, the distance between it and the center of the Sun sweeps out a constant area in a given amount of time.
• Kepler’s third law: For an object in a closed orbit around the Sun, the square of its period is proportional to the cube of the semimajor axis of its orbit:

Question 2

Which of the following statements about Kepler’s first law of planetary motion is not correct?

Answer 2

The orbit of the planets is an ellipse with one focus.

Question 3

Consider a moon that is 1.15 × 10^6 km from the planet it is orbiting. This moon makes one complete orbit every 27 days. What is the orbital period of a satellite orbiting the planet at a distance of 4.10 × 10^6 km?

Answer 3

181.8 d

Question 4

Which of the following is the best method to determine that the orbital radius and periods of Jupiter and Saturn are in agreement with Kepler’s laws? Use the subscript j for Jupiter and s for Saturn; r is the radius from the Sun to the planet and T represents the period.

Answer 4

Determine if the value of (rj / rs)3/2 is equal to Tj / Ts.

Question 5

Kepler’s work resulted in three laws of orbital motion. Which of the following is not true?

Answer 5

Kepler described and explained the motions of the planets known at that time.

Question 6

Consider Kepler’s second law of planetary motion. Which of the following is not correct?

Answer 6

A planet’s orbital speed is greater when it is farther away from the sun than when it is closer to the sun.

Question 7

Suppose that a new planet is discovered and its period is determined. The new planet’s distance from the Sun could be found using Kepler’s ________________

Answer 7

third law

Question 8

Consider Kepler’s third law of planetary motion. Which of the following is not correct?

Answer 8

There is a constant K such that T 2 = K R 3 for all objects orbiting a body.

Question 9

Planets at a greater distance from the Sun _________________.

Answer 9

have longer periods of revolution

Question 10

The moon has a period Tm equal to 28 days and an orbital radius rm equal to 3.8*10^5 km. What is the orbital radius of a satellite that travels around the Earth in 1 day?

Answer 10

4.12 × 10^4 km