With respect to the opening the height of the piston is 0/5 m . Pressure at the top is `P_(1)= P_(0) + (20 xx10N)/(0.5m^(2))`
where `P_(0)` is the atmospheric pressure . Pressure at the opening is `P_(2) = P_(0)`
From Bernoulli.s equation , we have
`P_(1) + rho gh+1/2 rho v_(1)^(2) = P_(2) +1/2 rho v_(2)^(2)`
Solving we get , `v_(2) = 3.3 m//s = v_(x) , ` say
` v_(y) = sqrt(2gh)`
` v = sqrt(v_(x)^(2)+v_(gamma)^(2)) = 4.56 m//s`
