Correct Answer - 2
`vt = 80 m ……(i)`
`t = sqrt((2h)/(g)) = sqrt((2 xx 20)/(10)) = 2` second ……`(ii)`
from `(i)` and `(ii)` equ.
`v = 40 m//s. ……(iii)`
`P_(0) + rhogh = P_(atm) + (1)/(2) rhov_(2) …...(iv)`
on solving `(iv)` equation
`P_(0) = 2.78 xx 10^(5) Nm^(-2) = (1.39)alpha xx 10^(5)`
`alpha = 2` Ans.