$1 \text{ MW} = \dots \text{ erg/s}$.

One astronomical unit is a distance equal to ...... $m$

The energy required to break one bond in $DNA$ is $10^{-20} \ J$. This value in $eV$ is nearly:

In a cesium clock,the time interval depends on which factors?

Write the unit of mass used for atoms and its definition.

It is estimated that per minute each $cm^2$ of the Earth receives about $2 \ cal$ $(1 \ cal = 4.18 \ J)$ of heat energy from the Sun. This is called the Solar constant. In $SI$ units,the value is: (in $W/m^2$)