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Q.
A solid cube and a solid sphere of the same material have equal surface area. Both are at the same temperature $120^{\circ}C$, then
Thermal Properties of Matter
Solution:
Rate of cooling of a body $R=\frac{\Delta \theta}{t}$
$=\frac{A \varepsilon \sigma\left(T^{4}-T_{0}^{4}\right)}{m c}$
$\Rightarrow R \propto \frac{A}{m} \propto \frac{\text { Area }}{\text { Volume }}$
$\Rightarrow $ For the same surface area. $R \propto \frac{1}{\text { Volume }}$
$\because$ Volume of cube $<$ Volume of sphere
$\Rightarrow R_{\text {Cube }}>R_{\text {Sphere }}$ i.e., cube, cools down with faster rate