Question

A horizontal water jet with a velocity of 10 m/s and cross-sectional area of 10 mm${}^2$ strikes a flat plate held normal to the flow direction. The density of water is 1000kg/$m^3$. The total force on the plate due to the jet is

• A. 100N
• B. 10 N
• C. 1 N
• D. 0.1 N

Answer 1

The correct option is C 1 N

The force is given by

F = $\rho$ aV${}^2$

$\Rightarrow F=1000\frac{kg}{m^3}\times 10m{m}^2\times (10\frac{m}{sec}{)}^2$

$\Rightarrow F=1000\frac{kg}{m^3}\times \frac{10m^2}{{10}^6}\times (10\frac{m}{sec}{)}^2$

$=\frac{1kg-m}{sec}$

= 1 N