Question

Assertion : The square of the period of revolution of a planet is proportional to the cube of the semi-major axis of the ellipse

Reason : Sun's gravitational field is inversely proportional to the square of its distance from the planet.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

Correct option (b) Both A and R are true but R is not correct explanation of A

Explanation :

To make our calculations easy, let's take the semi major axis of the ellipse be equal to the average distance of the sun from the planet. By applying Newton's law,