The reading of pressure metre attached with a closed pipe is 4.5 × 10^4 N / m^2. On opening the valve, water starts flowing and the reading of…

The reading of pressure metre attached with a closed pipe is $\displaystyle 4.5 \times 10^4 \mathrm{~N} / \mathrm{m}^2$. On opening the valve, water starts flowing and the reading of pressure metre falls to $\displaystyle 2.0 \times 10^4 \mathrm{~N} / \mathrm{m}^2$. The velocity of water is found to be $\displaystyle \sqrt{\mathrm{V}} \mathrm{m} / \mathrm{s}$. The value of V is $\displaystyle \_\_\_\_$.