physics : class11 Orbital Sector : Second Law of Kepler : Gravitation MCQ Questions and Answers
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Orbital Sector
MCQ questions and answers.
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MCQ Questions
1. According to Kepler's second law, the line joining a planet to the Sun sweeps out equal areas in
A.
equal intervals of time
B.
equal distances
C.
unequal intervals of time only
D.
one complete revolution only
Correct Answer:
equal intervals of time
Explanation:
Kepler's second law states that the radius vector from the Sun to the planet sweeps out equal areas in equal intervals of time.
2. If a planet sweeps an orbital sector of area 5 units in 2 days, what area will it sweep in the next 2 days?
A.
2.5 units
B.
5 units
C.
10 units
D.
20 units
Correct Answer:
5 units
Explanation:
Equal areas are swept in equal intervals of time, so the area swept in the next 2 days is also 5 units.
3. When a planet moves closer to the Sun in its elliptical orbit, its orbital speed generally
A.
increases
B.
decreases
C.
becomes zero
D.
remains exactly constant
Correct Answer:
increases
Explanation:
To sweep equal orbital sectors in equal times, the planet moves faster when it is nearer the Sun.
4. At which position in its orbit does a planet move fastest according to Kepler's second law?
A.
Nearest the Sun
B.
Farthest from the Sun
C.
At the center of the Sun
D.
At every point with the same speed
Correct Answer:
Nearest the Sun
Explanation:
The planet moves fastest at the point nearest the Sun so that equal areas are swept in equal times.
5. A planet sweeps areas A1 and A2 during two equal time intervals. According to Kepler's second law, the relation between them is
A.
A1 = A2
B.
A1 = 2A2
C.
A2 = 2A1
D.
A1 + A2 = 0
Correct Answer:
A1 = A2
Explanation:
Kepler's second law directly states that equal time intervals correspond to equal swept areas.
6. The area swept by the radius vector of a planet per unit time is called its
A.
areal velocity
B.
linear velocity
C.
angular displacement
D.
orbital radius
Correct Answer:
areal velocity
Explanation:
Areal velocity is the rate at which the radius vector sweeps out orbital area, and it remains constant according to Kepler's second law.
7. If a planet takes 4 days to sweep an orbital sector of area 12 units, its areal velocity is
A.
3 units per day
B.
4 units per day
C.
12 units per day
D.
48 units per day
Correct Answer:
3 units per day
Explanation:
Areal velocity equals swept area divided by time, so it is 12 divided by 4, or 3 units per day.
8. In equal time intervals, the orbital sectors swept by a planet around the Sun have
A.
equal areas
B.
equal radii
C.
equal arc lengths always
D.
equal angles always
Correct Answer:
equal areas
Explanation:
The key statement of Kepler's second law is that the orbital sectors swept in equal times have equal areas.
9. A planet moves from a farther point to a nearer point in its orbit while sweeping the same area in the same time. Its distance traveled along the orbit must generally
A.
increase
B.
decrease to zero
C.
remain zero
D.
become unrelated to its speed
Correct Answer:
increase
Explanation:
Nearer the Sun, the planet moves faster to sweep the same area in the same time, so it generally travels a greater distance along its orbit.
10. If the areal velocity of a planet is constant, the ratio of areas swept in 3 days and 6 days is
A.
1:2
B.
2:1
C.
1:1
D.
3:1
Correct Answer:
1:2
Explanation:
With constant areal velocity, swept area is proportional to time. Therefore, the areas in 3 days and 6 days are in the ratio 3:6, or 1:2.
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