Define mass. Write the unit of mass used in nuclear physics and its value in kilograms.

(N/A) Mass is defined as the quantity of matter contained in a body.
In nuclear physics,the unit used to measure mass is the unified atomic mass unit,denoted by $u$ or $amu$.
$1$ unified atomic mass unit $(1 \ u)$ is defined as $\frac{1}{12}$ of the mass of a carbon-$12$ atom $(^{12}_{6}C)$.
The value of $1 \ u$ is approximately $1.66 \times 10^{-27} \ kg$.