physics : class11 Orbital Speed : Second Law of Kepler : Gravitation MCQ Questions and Answers
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Orbital Speed
MCQ questions and answers.
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MCQ Questions
1. According to Kepler's second law, a planet moves fastest when it is at which position in its orbit around the Sun?
A.
Perihelion
B.
Aphelion
C.
The midpoint of its orbit
D.
The position farthest from the orbital plane
Correct Answer:
Perihelion
Explanation:
Kepler's second law implies that a planet moves faster when it is closer to the Sun, so its maximum orbital speed occurs at perihelion.
2. At which position is a planet's orbital speed minimum?
A.
Perihelion
B.
Aphelion
C.
The point directly above the Sun
D.
Everywhere in the orbit
Correct Answer:
Aphelion
Explanation:
A planet is farthest from the Sun at aphelion and moves with its minimum orbital speed there.
3. A planet sweeps out equal areas in equal intervals of time. If it is closer to the Sun, how does its orbital speed compare with its speed when it is farther away?
A.
It is greater
B.
It is smaller
C.
It is zero
D.
It is always the same
Correct Answer:
It is greater
Explanation:
To sweep out the same area in the same time when closer to the Sun, the planet must move through a greater distance and therefore have a greater orbital speed.
4. A planet has an orbital speed of 20 km/s at aphelion. Its speed at perihelion is most likely:
A.
Less than 20 km/s
B.
Equal to 20 km/s
C.
Greater than 20 km/s
D.
Zero
Correct Answer:
Greater than 20 km/s
Explanation:
The planet moves faster at perihelion than at aphelion because it is closer to the Sun.
5. At perihelion, the distance of a planet from the Sun is smallest. Its orbital speed at this point is:
A.
Maximum
B.
Minimum
C.
Always zero
D.
Unrelated to its distance from the Sun
Correct Answer:
Maximum
Explanation:
According to Kepler's second law, the orbital speed is greatest when the planet is closest to the Sun.
6. If a planet moves more slowly as it travels away from the Sun, which principle directly explains this change in orbital speed?
A.
Equal areas are swept in equal times
B.
The planet has no gravitational force
C.
The planet's mass becomes zero
D.
The orbit has no fixed direction
Correct Answer:
Equal areas are swept in equal times
Explanation:
Kepler's second law states that equal areas are swept in equal times. Thus, as the distance from the Sun increases, the planet's speed decreases.
7. A planet travels from perihelion toward aphelion. What happens to its orbital speed?
A.
It generally decreases
B.
It generally increases
C.
It becomes infinite
D.
It remains zero
Correct Answer:
It generally decreases
Explanation:
The planet moves away from the Sun on its way from perihelion to aphelion, and its orbital speed decreases.
8. Two equal time intervals are considered for a planet, one near perihelion and one near aphelion. During which interval does the planet cover a greater distance along its orbit?
A.
Near perihelion
B.
Near aphelion
C.
The distances are always zero
D.
The distance is always the same because the time intervals are equal
Correct Answer:
Near perihelion
Explanation:
The planet's orbital speed is greater near perihelion, so it covers a greater distance during an equal time interval.
9. If a planet's orbital speed at perihelion is 30 km/s, which statement about its speed at aphelion is correct?
A.
It is less than 30 km/s
B.
It is greater than 30 km/s
C.
It is exactly 30 km/s for every orbit
D.
It must be zero
Correct Answer:
It is less than 30 km/s
Explanation:
The planet is farther from the Sun at aphelion, where its orbital speed is lower than at perihelion.
10. Why must a planet move faster when it is closer to the Sun in order to obey Kepler's second law?
A.
A shorter radius requires greater speed to sweep the same area in the same time
B.
The planet becomes heavier near the Sun
C.
The Sun stops attracting the planet near aphelion
D.
The planet changes its size near perihelion
Correct Answer:
A shorter radius requires greater speed to sweep the same area in the same time
Explanation:
The swept area depends on both distance from the Sun and the distance traveled. With a smaller radius, greater orbital speed is needed to sweep the same area in the same time.
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