A rectangular vessel when full of water takes 10 minutes to be emptied through an orifice in its bottom. How much time will it take to be emptied when half filled with water

Options

A. 3 min
B. 5 min
C. 7 min
D. 9 min

Answer

C

Explanation

Time taken to empty a vessel of height h, `t=sqrt(2h//g))`
Time taken in emptying a vessel of height h/2.
`t'=sqrt((2h//2)/(g))=sqrt((h)/(g)) therefore (1)/(sqrt2) or t' (t)/(sqrt2)=t'=(t)/(sqrt2)=(10)/(sqrt2)approx7"min"`