In an experment ot verify Newton's law of cooling, a graph is plotted between, the temperature difference $(\Delta T )$ of the water and surroundings and time as shown in figure. The initial temperature of water is taken as $80^{\circ} \,C$. The value of $t _{2}$ as mentioned in the graph will be...........

A sphere at temperature $600\,K$ is placed in an environment of temperature is $200\,K$ . Its cooling rate is $H$ . If its temperature reduced to $400\,K$ then cooling rate in same environment will become

Which of the following statements is true/correct

Ice is used in a cooler in order to cool its contents. Which of the following will speed up the cooling process?

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 $sec$) will it take to cool from $71\,^{\circ} C$ to $69\,^{\circ} C ?$

On what does the proportionality constant depends given in Newton's law of cooling.