$A$ body takes $4$ minutes to cool from $100^{\circ}C$ to $70^{\circ}C$. To cool from $70^{\circ}C$ to $40^{\circ}C$ it will take ........ $\text{min.}$ (room temperature is $15^{\circ}C$)

$A$ block of metal is heated to a temperature much higher than the room temperature and placed in an evacuated cavity. Which curve correctly represents the rate of cooling? ($T$ is the temperature of the block and $t$ is the time.)

Hot water cools from $80^{\circ} C$ to $60^{\circ} C$ in $1$ minute. How long will it take to cool from $60^{\circ} C$ to $50^{\circ} C$ (in $s$)? (Room temperature $= 30^{\circ} C$)

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 $69\,^{\circ}C$?

$A$ suspended sphere has density $d$ and specific heat $s$. The radius of the sphere is $r$. The temperature difference between the sphere and the surroundings $(\Delta \theta)$ is very small. If the temperature of the surroundings is $\theta_0$,then the rate of cooling of the sphere will be .......