Question

There are two spherical balls $A$ and $B$ of the same material with same surface finish but the radius of $A$ is half Type equation here.that of $B$. It $A$ and $B$ are heated to the same temperature and allowed to cool then

• A. rate of cooling of both is same
• B. rate of cooling of $A$ is $4$ times that of $B$
• C. rate of cooling of $A$ is twice that of $B$
• D. rate of cooling of $A$ is $1 / 4$ times that of $B$

Answer 1

Answer: (D)

Rate of cooling $\propto$ area of the body
$\propto r^{2}$
since, radius of $A$ is $\frac{1}{2}$ that of $B$, rate of cooling $A$ is $\frac{1}{4}$ that of $B$.