**With what velocity does water flow out of an orifice in a tank with gauge pressure 4x****10 ^{5} N/m^{2} before the flow starts? Density of water = 1000 kg/m^{3}**

**Correct answer= 28.28 m/s**

**Explaination**

**Given:: **p - p_{0} = 4 × 10^{5} Pa, ρ = 10^{3} kg/m^{3}

If the orifice is at a depth h from the water surface in a tank, the gauge pressure there is

p - p_{0} = hρg ....(1)

By Toricelli’s law of efflux, the velocity of efflux,

v = \(\sqrt{2gh}\) ...(2)

Substituting for h from Eq.(1),

v = \( \sqrt{2g{p - p_0)\over rhog}} = \sqrt{{2p - p_0)\over \rho}} \)

=\(\sqrt{\frac{2(4\times 10^5)}{10^3}}=20\sqrt2\) =28.28 m/s