Fluid Mechanics

At two points on a horizontal tube of varying cross-section the radii are 1 cm and $\mathbf{0 . 4 ~ c m}$, velocities of fluid are $\mathrm{V}_1, \mathrm{~V}_2$ and pressure difference ( $P_1-P_2$ ) between these points is 4.9 cm of water. The value of $\sqrt{V_2^2-V_1^2}$ is ( $\mathrm{g}=$ acceleration due to gravity $\mathrm{g}=980 \mathrm{~cm} / \mathrm{s}^2$ )