Question

Kepler's third law is known as

• A. None of the above
• B. Law of periods
• C. Law of orbits
• D. Law of gravity

Answer 1

Answer: (B)

Law of periods

Answer 2

Kepler's laws of planetary motion describe the motion of planets around the Sun.

• Kepler's First Law: The Law of Orbits states that all planets move in elliptical orbits with the Sun at one of the two foci.
• Kepler's Second Law: The Law of Areas states that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
• Kepler's Third Law: The Law of Periods states that the square of the orbital period ($T$) of a planet is directly proportional to the cube of the semi-major axis ($a$) of its orbit. Mathematically, $T^2 \propto a^3$. Therefore, Kepler's third law is known as the Law of Periods.