32
QuizMultiple Choice

Cumulative Exam — Cumulative exam

Question 32 • KY-Earth, Space Science B

Which statements describe the motion of a planet according to Kepler’s second law? Check all that apply.The speed of a planet varies as it moves in its orbit. The speed of a planet is constant as it moves in its orbit.A planet travels the same distance along its orbit in equal units of time.A planet sweeps out an equal area in equal units of time.A planet’s orbit is a circle centered on the Sun.A planet’s orbit is an ellipse with the Sun at one focus.

Answer
A
The speed of a planet varies as it moves in its orbit.
B
The speed of a planet is constant as it moves in its orbit.
C
A planet travels the same distance along its orbit in equal units of time.
D
A planet sweeps out an equal area in equal units of time.
E
A planet’s orbit is a circle centered on the Sun.
F
A planet’s orbit is an ellipse with the Sun at one focus.

Explanation

Kepler’s second law says a planet sweeps out equal areas in equal amounts of time, so D is correct. To sweep out the same area in the same time, the planet must move faster when it is closer to the Sun and slower when it is farther away; therefore its speed varies, making A correct. Equal distances in equal times would mean constant speed, which is not what the law states.

AI-written and checked against the verified answer.

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