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

A body cools in a surrounding which is at a constant temperature of ${\theta _0}$. Assume that it obeys Newton's law of cooling. Its temperature $\theta $ is plotted against time $t$ . Tangents are drawn to the curve at the points $P(\theta = {\theta _1})$ and $Q(\theta = {\theta _2})$. These tangents meet the time axis at angles of ${\varphi _2}$and ${\varphi _1}$, as shown

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

Instantaneous temperature difference between cooling body and the surroundings obeying Newton's law of cooling is $\theta$. Which of the following represents the variation of $\ln \theta$ with time $t$ ?

Draw the graph that represents the cooling of hot water with time. Is the slope of the above graph positive or negative ?