Q. Assuming the mass of earth as $6.64 \times 10^{24}$ kg and the average mass of the atoms that makes up earth as 40 u (atomic mass unit), the number of atoms in the earth is approximately
A) $10^{30}$
B) $10^{40}$
C) $10^{50}$
D) $10^{60}$
Explanation
(c) 1amu (or 1 u)=$1.6\ \times \ 10^{- 27}\ kg$
40 u=$40\ \times \ 1.6\ \times \ \ 10^{- 27}\ kg$
Number of atoms in earth
$= \frac{6.64\ \times \ 10^{24}}{40\ \times 1.6\ \times 10^{- 27}}$ = $10^{50}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.