Question

What is the ratio of the gravitational pull of the sun on the moon to that of the earth on the moon?

• A. 6
• B. 4
• C. 2.25
• D. 1/4

Answer 1

Answer: (C)

Gravitational force is given by $F=G{m}_1{m}_2/r^2$ where $m_1$ and $m_2$ are the masses of the two objects, r is the distance between their centers of gravity, and G is the universal gravitational constant.

$\frac{ForceexertedonMoon}{ForceexertedonEarth}=\frac{G{m}_{m}m/r_m^2}{G{m}_{e}m/r_e^2}=\frac{m_m{r}_e^2}{m_e{r}_m^2}$

$\frac{ForceexertedonMoon}{ForceexertedonEarth}=\frac{2\times {10}^{30}\times (3.9\times {10}^5{)}^2}{6\times {10}^{24}\times (1.5\times {10}^8{)}^2}=\frac{3.042\times {10}^{41}}{1.35\times {10}^{41}}=2.25$