Q. A bucket full of hot water is kept in a room. It cools from $75℃$ to 70$℃$ in $t_{1}$ minutes, from 70$℃$ to 65$℃$ in $t_{2}$ minutes and from 65$℃$ to 60$℃$ in $t_{3}$ minutes. Then,
A) $t_{1} < t_{2} < t_{3}$
B) $t_{1} = t_{2} = t_{3}$
C) $t_{1} < t_{2} > t_{3}$
D) $t_{1} > t_{2} > t_{3}$
Explanation
(a) According to Newton’s law of cooling we have, rate of cooling $\propto$ temperature difference between the liquid and surrounding.
As temperature difference decreases gradually, time taken to cool increases
$ie.,$ $t_{1} < t_{2} < t_{3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.