It is estimated that each $cm^2$ of Earth receives about $2 \text{ calorie}$ of heat energy per minute from the Sun. This is called the solar constant. The value of the solar constant in $S.I.$ units is:

The unit of length convenient on the atomic scale is known as an $\mathring{A}$ and is denoted by $\mathring{A}: 1 \mathring{A} = 10^{-10} \, m$. The size of a hydrogen atom is about $0.5 \mathring{A}$. What is the total atomic volume in $m^{3}$ of a mole of hydrogen atoms?

Find the rate of change of the volume of a sphere with respect to its surface area when the radius is $2 \ cm$.

$0.1 \, Pa = \dots \, Nm^{-2} = \dots \, \text{dyne} \, cm^{-2}$.

Estimate the average mass density of a sodium atom assuming its size to be about $2.5 \; \mathring{A}$. (Use the known values of Avogadro's number and the atomic mass of sodium). Compare it with the mass density of sodium in its crystalline phase: $970 \; kg \; m^{-3}$. Are the two densities of the same order of magnitude? If so,why?

In a new system,the unit of mass is $10 \ kg$,the unit of length is $5 \ m$,and the unit of time is $10 \ s$. Then,in this new system,$20 \ g/cm^3$ is equal to: