Question

In terms of energy $1$ amu is equal to:

• A. 100 J
• B. 931.1 kcal
• C. 931.1 MeV
• D. $10^{7}erg$

Answer 1

Answer: (C)

$1amu=1.67\times 10^{-24}g$
Energy equivalent to this mass can be calculated by using the relation;
$E=m{c}^2$
Here $m=1.67\times 10^{-24}g$
$c=3\times 10^{10}cm{\sec }^{-1}$
$\therefore E=1.67\times 10^{-24}\times {\left(3\times 10^{10}\right)}^2$ ergs
$=\frac{1.503\times 10^{-3}}{10^7}J$
$=1.503\times 10^{-10}J$
Now, $1.6\times 10^{-19}J=1eV$
$1J=\frac{1}{1.6\times 10^{-19}}eV$
$=6.25\times 10^{18}eV$
$\therefore 1.503\times 10^{-10}J$
$=6.25\times 10^{18}\times 1.503\times 10^{-10}eV$
$=9.393\times 10^{8}eV$
$\therefore 1amu=939.3MeV$