Gravitation Question 8
Question 8 - 25 January - Shift 2
Every planet revolves around the sun in an elliptical orbit :
A. The force acting on a planet is inversely proportional to square of distance from sun.
B. Force acting on planet is inversely proportional to product of the masses of the planet and the sun
C. The centripetal force acting on the planet is directed away from the sun.
D. The square of time period of revolution of planet around sun is directly proportional to cube of semi-major axis of elliptical orbit.
Choose the correct answer from the options given below :
(1) A and D only
(2) C and D only
(3) B and C only
(4) A and C only
Show Answer
Answer: (1)
Solution:
Formula: Kepler’s Laws
$F=\frac{Gm_1 m_2}{r^{2}}$
$\Rightarrow F \propto \frac{1}{r^{2}}$
$\Rightarrow F \propto m_1 m_2$
$\Rightarrow$ This force provides centripetal force and acts
towards sun
$\Rightarrow T^{2} \propto a^{3}$ (Kepler’s third law)
