In astronomy and classical physics, Kepler’s laws of planetary motion describe the motions of the planets in the solar system. They were discovered by German astronomer Johannes Kepler, who used the observations of 16th-century Danish astronomer Tycho Brahe to publish his first two laws in 1609 and a third rule nearly a decade later in 1618. Kepler never assigned a numerical value to these rules or separated them from his other findings.

The three laws of planetary motion established by Kepler are as follows:

 (1) All planets move in elliptical orbits around the Sun, with the Sun as one of the foci. 

(2) A radius vector connecting any planet to the Sun sweeps out the same amount of area in the same amount of time. 

(3) The cubes of the planets’ mean distances from the Sun are directly proportional to the squares of their sidereal periods (of revolution).

MCQs

1. According to which law, the line connecting any planet to the sun covers equal areas at equal time intervals?

1. 1. Gravitational law
   2. The Periodic Law
   3. The Law of areas
   4. The orbital law

Answer: Correct option will be: (3) The Law of areas

2. The sun is positioned ____ of the planet’s orbit, according to Kepler’s law of orbit.

1. 1. in the center 
   2. in one of the foci 
   3. in both foci 
   4. along the semi-minor axis

Answer: Correct option will be: (2) in one of the foci

Reason: Every planet circles around the sun in an elliptical orbit, with the sun at one of the foci, according to Kepler’s law of orbit.

3. The smallest and greatest distances a planet travels around the sun are r and R, respectively. If the planet’s minimum speed on its journey is v0, its maximum speed is:

1. 1. V0Rr
   2. V0rR
   3. V0R2r2
   4. V0r2R2

Answer: Correct option will be: (1)V0Rr

4. If the time of revolution of a satellite is T, then the potential energy will be proportional to

1. 1. T1/3
   2. T3
   3. T-2/3
   4. T-4/3

Answer: Correct option will be: (3) T-2/3.

5. The work done by the sun’s gravitational attraction on a planet as it moves from perihelion to aphelion is:

1. 1. 0
   2. Negative
   3. Positive
   4. Cannot be said

Answer: Correct option will be: (2) Negative

6. A satellite’s period in a circular orbit near a planet is unaffected by

1. 1. Planet’s mass
   2. Planet’s radius
   3. Satellite’s mass
   4. All the mentioned

Answer: Correct option will be: (3) satellite’s mass.

7. Which of the mentioned shapes has an eccentricity of zero?

1. 1. Straight line
   2. Big ellipse
   3. Circle
   4. Small ellipse

Answer: Correct option will be: (3) Circle.

8. What is the equivalent of an Astronomical Unit?

1. 1. Sun and Neptune
   2. Sun and Earth
   3. Earth and moon 
   4. Sun and mercury

Answer: Correct option will be: (2) Sun and Earth.

9. If a planet is farther away from the sun, the time taken by that planet to orbit the sun will be:

1. 1. Longer
   2. Shorter

Answer: Correct option will be: (1)Longer.

10. What are the parameters that Kepler’s law of period relates to?

1. 1. The semi-minor axis and the time period
   2. Eccentricity and the time period
   3. The semi-major axis and the time period
   4. The planet’s area of sweep and the time period

Answer: Correct option will be: (3) The semi- major axis and the time period.

11. A planet’s velocity remains constant during its elliptical orbital course.

1. 1. True 
   2. False

Answer: Correct option will be: (2) False

12. Calculations of the orbit of which astronomical body revealed the elliptical orbits of planets?

1. 1. Mercury
   2. Earth
   3. Earth’s moon
   4. Mars

Answer: Correct option will be: (4) Mars

13. What is the eccentricity of the parabolic orbit?

1. 1. 0
   2. -1
   3. 1

Answer: Correct option will be: (3)1

14. What is the name of the planet’s closest approach to the sun?

1. 1. Aphelion
   2. Daphelion
   3. Herihelion
   4. Perihelion

Answer: Correct option will be: (4) Perihelion

Reason: Perihelion refers to the point when the planet is closest to the sun, whereas aphelion refers to the point where the planet is furthest from the sun.

15. What would be the duration of an year if the distance between the earth and the sun becomes one- fourth of the present distance?

1. 1. One- eighth times of the present year
   2. One- sixth times of the present year
   3. One-tenth times of the present year
   4. Half of the present year.

Answer: Correct option will be: (1) one- eighth time of the present year.

16. What will be the total number of days in an year if the distance between the sun and the earth is halved?

1. 1. 129
   2. 730
   3. 182
   4. 786

Answer: Correct option will be: (1)129.

17.A planet orbits the sun at three times the speed of the earth. If rp and re are the planet’s and Earth’s respective orbital radii, then:

1. 1. re3=9rp3
   2. re3=8rp3
   3. re3=3rp3
   4. re3=13rp3

Answer: Correct option will be re3=9rp3

18. According to the first law of Kepler, the shape of the orbit of the planets are:

1. 1. Perfect circle
   2. Square
   3. Triangle
   4. Ellipse

Answer: Correct option will be: (4) Ellipse

Reason: According to the first law of Kepler the orbits of the planets have an oval or ellipse shape.

19. According to the first law of Kepler the summation of the distances between two foci will be:

1. 1. 0
   2. constant
   3. 1

Answer: Correct option will be: (3) constant.

20. What does Kepler’s second law state?

1. 1. The sun is at one of the foci of all the planets’ eccentric orbits around the sun.
   2. The radius vector traced from the sun to the planet sweeps out the same amount of area in the same amount of time.
   3. The cube of a planet’s semi-major axis is precisely proportional to the square of its time period of revolution around the sun in an elliptical orbit.
   4. All of the mentioned.

Answer: Correct option will be: (2) The radius vector traced from the sun to the planet sweeps out the same amount of area in the same amount of time.