Question

A rubber pipe with a diameter of 10 cm is connected to a nozzle 2 cm in diameter. Water flowing through the pipe at a speed of 0.6 ms${}^{-1}$ comes out like a jet through the nozzle. The backward force of the nozzle is about:

• A. 7.7 N
• B. 67.9 N
• C. zero
• D. 2.8 N

Answer 1

The correct option is B 67.9 N

Diameter $D$ of pipe $=10$cm

Diameter $d$ of nozzle $=2$cm

Velocity of water $v=0.6m/s$

Reaction force$=v\times \frac{dm}{dt}$ (rate of mass flow)

$=>F=0.6\times \frac{{10}^2}{2^2}\times {0.05}^2\times 0.6\times 1000\times \frac{22}{7}=67.9N$