Question

The mass of the moon is 1% of mass of the earth.The ratio of gravitational pull of earth on moon to that of moon on earth will be:

• A. 1 : 1
• B. 1 : 10
• C. 1 : 100
• D. 2 : 1

Answer 1

The correct option is A 1 : 1

Mass of earth be $M$ and mass of moon be $m.$

Let the distance between moon and earth be $r$

Now force exerted by earth on moon, $F_e=\frac{GMm}{r^2}$

Force exerted by moon on earth $F_m=\frac{GmM}{r^2}$

$F_e:F_m=1:1$

This can also be solved by newton's 3rd law of motion.