Question

Water jet is coming out of a hose pipe of diameter $20cm$ with speed $20cm/sec$. It strike a man inelastically. Find the force exerted by water jet on the person.

• A. $5.04N$
• B. $1.26N$
• C. $2.52N$
• D. $9.4N$

Answer 1

The correct option is B $1.26N$

F $=$ density $\times$ area $\times velocit{y}^2$

Convert V to m/s:

$20/100=0.2$

$=0.2m/s$

Density of water $=1000\frac{kg}{m^3}$

Convert the diameter length to be in meters :

$20/100=0.2$

Area of the outlet :

$3.142\times (0.2/2{)}^2=3.142\times {0.1}^2=0.03142$

Doing the substitution :

$F=1000\times 0.03142\times {0.2}^2=1.2568$