Question

A cylidrical drum, open at the top, contains 30 litres of water. It drains out through a small opening at the bottom. 10 litres of water comes out in time $t_1$, the next 10 litres in further time $t_2$ and the last 10 litres 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. $t_2<t_1=t_3$

Answer 1

The correct option is C $t_1<t_2<t_3$

Using the torricelli's theorem we know that the velocity of efflux is given as $\sqrt{2gh}$. Thus we see that the velocity is dependent upon height. As the height decreases the velocity of efflux will also decrease, so time taken by water to drain out of the drum will increase.
Thus option C is correct.