A stream of water flowing horizontally with a speed of $15 {\mathrm{ms}}^{-1}$ gushes out of a tube of cross-sectional area ${10}^{-2} {\mathrm{m}}^2$, and hits a vertical wall normally. Assuming that it does not rebound from the wall, the force exerted on the wall by the impact of water is

Here $\mathrm{\nu }=15 {\mathrm{ms}}^{-1}$ , Area of cross section $\mathrm{A}={10}^{-2} {\mathrm{m}}^2$, Density of water $\mathrm{\rho }={10}^3 \mathrm{kg} {\mathrm{m}}^{-3}$

Mass of water hitting the wall per second $=\mathrm{\rho }\times \mathrm{A}\times \mathrm{\nu }={10}^3 {\mathrm{kgm}}^{-3}\times {10}^{-2} {\mathrm{m}}^2\times 15 {\mathrm{ms}}^{-1}=150 {\mathrm{kgs}}^{-1}$

Force exerted on the wall $=$ Momentum loss of water per second 

$=150 {\mathrm{kgs}}^{-1}\times 15 {\mathrm{ms}}^{-1}=2250 \mathrm{N}=2.25\times {10}^3 \mathrm{N}$