Q. A cylinder drum, open at the top, contains 15 L of water. It drains out through a small opening at the bottom. 5 L of water comes out in time $t_{1}$, the next 5 L in further time $t_{2}$ and the last 5 L in further time $t_{3}$. 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) If $h$ is the initial height of liquid in drum above the small opening, then velocity of efflux, $v = \sqrt{2\ gh}$. As the water drains out, $h$ decreases, hence $v$ decreases. This reduces the rate of drainage of water. Due to which, as the drainage continues, a longer time is required to drain out the same volume of water
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.