Thermal Properties Of Matter Ques 45
45. A body cools from $50.0^{\circ} C$ to $48^{\circ} C$ in $5 $ $s$. How long will it take to cool from $40.0^{\circ} C$ to $39^{\circ} C$ ? Assume the temperature of surroundings to be $30.0^{\circ} C$ and Newton’s law of cooling to be valid.
[1994]
(a) $2.5 $ $s$
(b) $10 $ $s$
(c) $20 $ $s$
(d) $5 $ $s$
Show Answer
Answer:
Correct Answer: 45.(b)
Solution:
- (b) Rate of cooling $\propto$ temperature difference between system and surrounding.
As the temperature difference is halved, so the rate of cooling will also be halved.
So time taken will be doubled
$t=2 \times 5$ sec $=10$ sec.
BETA
