First slide

Conduction

Question

A solid cube and a solid sphere of the same material have equal surface area. Both are at the same temperature $120^{0} C$ , then

Moderate

A

Both the cube and the sphere cool down at the same rate
B

The cube cools down faster than the cube
C

The sphere coolds down faster than the cube
D

Whichever is having more mass will cool down faster

Solution

Rate of cooling of a body R = $\frac{∆ θ}{t} = \frac{Aεσ (T^{4} - {T_{0}}^{4})}{mc}$
$\Rightarrow R directly proportional to \frac{A}{m} directly proportional to \frac{Area}{Volume}$
Volume of cube < Volume of sphere
$\Rightarrow R_{cube} > R_{sphere} i . e ., cube, cools down with faster rate$

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