Two bottles $A$ and $B$ have radii $R_{A}$ and $R_{B}$ and heights $h_{A}$ and $h_{B}$ respectively, with $R_{B}=2 R_{A}$ and $h_{B}=2 h_{A}$. These are filled with hot water at $60^{\circ} C$. Consider that heat loss for the bottles takes place only from side surfaces. If the time, the water takes to cool down to $50^{\circ} C$ is $t_{A}$ and $t_{B}$ for bottles $A$ and $B$, respectively. Then, $t_{A}$ and $t_{B}$ are best related as
$t_{A}=t_{B}$
$t_{B}=2 t_{A}$
$t_{B}=4 t_{A}$
$t_{B}=t_{A} / 2$
Draw the graph that represents the cooling of hot water with time. Is the slope of the above graph positive or negative ?
Hot water cools from ${60^o}C$ to ${50^o}C$ in the first $10$ minutes and to ${42^o}C$ in the next $10$ minutes. The temperature of the surrounding is ......... $^oC$
A body cools from $80^{\circ}\,C$ to $60^{\circ}\,C$ in $5$ minutes. The temperature of the surrounding is $20^{\circ} C$. The time it takes to cool from $60^{\circ}\,C$ to $40^{\circ}\,C$ is........... $s$
A metallic sphere cools from $50^{\circ} C$ to $40^{\circ} C$ in $300 \,s.$ If atmospheric temperature around is $20^{\circ} C ,$ then the sphere's temperature after the next $5$ minutes will be close to$.....C$
A sphere, a cube and a disc all of the same material, quality and volume are heated to $600\,^oC$ and left in air. Which of these will have the lowest rate of cooling ?