What is Newton's law of cooling used to determine in a laboratory?

For a system where Newton's law of cooling is applicable,the initial rate of cooling is $R \ ^\circ C/sec$. Find the time when the temperature difference $\Delta T_0$ (initial temperature difference) is reduced to half.

The temperature of a body falls from $50^oC$ to $40^oC$ in $10$ minutes. If the temperature of the surroundings is $20^oC$,then the temperature of the body after another $10$ minutes will be ........ $^oC$.

Two circular discs $A$ and $B$ with equal radii and equal mass are blackened. They are heated to the same temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

$A$ pan filled with hot food cools from $94\,^{\circ}C$ to $86\,^{\circ}C$ in $2$ minutes when the room temperature is at $20\,^{\circ}C$. How long (in $s$) will it take to cool from $71\,^{\circ}C$ to $69\,^{\circ}C$?

$A$ system $S$ receives heat continuously from an electrical heater of power $10 \ W$. The temperature of $S$ becomes constant at $50^{\circ}C$ when the surrounding temperature is $20^{\circ}C$. After the heater is switched off, $S$ cools from $35.1^{\circ}C$ to $34.9^{\circ}C$ in $1 \ minute$. The heat capacity of $S$ is........ $J/^{\circ}C$.