Question:
The force with which the earth attracts an object is called the weight of the object.
Calculate the weight of the moon from the following data: The universal constant of gravitation $G=$ $6.67 \times 10^{-11} \mathrm{~N}-\mathrm{m}^{2} / \mathrm{kg}$, mass of the moon $=7.36 \times 10^{22} \mathrm{~kg}$, mass of the earth $=6 \times 10^{24} \mathrm{~kg}$ and the distance between the earth and the moon $=3.8 \times 10^{5} \mathrm{~km}$.
Solution:
$W_{M}=F=\frac{G M_{e} M_{M}}{R^{2}}$
$=\frac{6.67 \times 10^{-11} \times 6 \times 10^{24} \times 7.36 \times 10^{22}}{\left(3.8 \times 10^{5} \times 10^{3}\right)^{2}}$
$=2.03 \times 10^{20} \mathrm{~N}$.
$F \approx 2 \times 10^{20} \mathrm{~N}$