1. According to Kepler's law of areas, the line joining a planet and the Sun sweeps out
A.
Equal areas in equal intervals of time
B.
Equal distances in equal intervals of time
C.
Unequal areas in equal intervals of time
D.
Equal areas in unequal intervals of time
Correct Answer:
Equal areas in equal intervals of time
Explanation:
Kepler's second law states that the radius vector joining the Sun and a planet sweeps out equal areas in equal intervals of time.
2. Kepler's law of areas is also known as
A.
The law of orbits
B.
The law of periods
C.
The law of equal areas
D.
The law of universal gravitation
Correct Answer:
The law of equal areas
Explanation:
Kepler's second law is commonly called the law of equal areas because equal areas are swept out in equal times.
3. When a planet moves closer to the Sun, its orbital speed generally
A.
Increases
B.
Decreases
C.
Becomes zero
D.
Remains exactly constant
Correct Answer:
Increases
Explanation:
To sweep out equal areas in equal times, the planet must move faster when it is closer to the Sun.
4. When a planet is farther from the Sun, its orbital speed is generally
A.
Greater than when it is closer
B.
Less than when it is closer
C.
Always zero
D.
Independent of its distance from the Sun
Correct Answer:
Less than when it is closer
Explanation:
The law of areas requires the planet to move more slowly at greater distances from the Sun so that equal areas are swept in equal times.
5. If a planet sweeps an area of 20 square units in 2 days, how much area will it sweep in 6 days?
A.
20 square units
B.
40 square units
C.
60 square units
D.
120 square units
Correct Answer:
60 square units
Explanation:
The area swept is proportional to time. Since 6 days is three times 2 days, the swept area is 3 times 20, or 60 square units.
6. The areal velocity of a planet is defined as the rate at which the radius vector sweeps out
A.
Distance
B.
Area
C.
Speed
D.
Time
Correct Answer:
Area
Explanation:
Areal velocity is the area swept out by the radius vector per unit time, written as dA/dt.
7. For a planet orbiting the Sun, the areal velocity is
A.
Constant
B.
Always increasing
C.
Always decreasing
D.
Zero at all points
Correct Answer:
Constant
Explanation:
Kepler's law of areas states that equal areas are swept in equal times, so the areal velocity remains constant.
8. In Kepler's law of areas, the radius vector is the line joining the
A.
Planet and another planet
B.
Sun and the planet
C.
Earth and the Moon
D.
Sun and the nearest star
Correct Answer:
Sun and the planet
Explanation:
The radius vector in this law is the line segment joining the Sun to the planet.
9. If equal areas are swept by a planet in equal times, the planet's areal velocity is
A.
Uniform
B.
Variable
C.
Negative
D.
Infinite
Correct Answer:
Uniform
Explanation:
Equal area swept per equal time interval means that the area swept per unit time is constant, or uniform.
10. A planet sweeps 15 square units in 3 hours. According to the law of areas, the area swept in 1 hour is
A.
3 square units
B.
5 square units
C.
15 square units
D.
45 square units
Correct Answer:
5 square units
Explanation:
The areal velocity is 15 divided by 3, which equals 5 square units per hour. Therefore, the area swept in 1 hour is 5 square units.
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