Question

g. The mass of the earth is 6 x 10²⁴ kg. The distance between the earth and the Sun is 1.5x 10¹¹ m. If the gravitational force between the two is 3.5 x 10²² N, what is the mass of the Sun?

Answer 1

the mass of the earth, m = 6 × 10²⁴ kg 
Assume the mass of the sun is M 
distance between earth and sun , r = 1.5 × 10¹¹ m
force between sun and earth , F = 3.5 × 10²²  N
use gravitational force formula,
 F = GMm/r²
3.5 × 10²² = 6.67 × 10⁻¹¹ × 6 × 10²⁴ M/(1.5 × 10¹¹)² 
3.5 × 10²² × 2.25 × 10²²/(6.67 × 6 × 10¹³) = M
M = 0.196 × 10³¹ kg 

hence, mass of the sun is 1.96 × 10³⁰ kg