Question

A stream of water flowing horizontally with a speed of $15$ $m{s}^{-1}$ gushes out of a tube of cross-sectional area ${10}^{-2}$ $m^2$, and hits a vertical wall nearby. What is the force exerted on the wall by the impact of water, assuming it does not rebound ?

Answer 1

The horizontal speed of the stream is,$v=15m/s$

The area of cross-section of the tube, $A={10}^{-2}{m}^2$

The Density of water is,$={10}^{3}kg/m^3$

The volume of water coming out from the pipe per second,

$V=Av=15\times {10}^{-2}{m}^3/s$

Mass of water flowing out through the pipe per second = $density\times Volume=150kg/s$

Since the water does not rebound from the wall, the force exerted by the water on the wall is given by:

$F=Rateofchangeofmomentum=\frac{P}{t}$

$F=\frac{mv}{t}$

for $t=1s$

$F=150\times 15=2250N$