10.16 The cylindrical tube of a spray pump has a cross-section of 8.0 cm2 one end of which has 40 fine holes each of diameter 1.0 mm. If the liquid flow inside the tube is 1.5 m min–1, what is the speed of ejection of the liquid through the holes?

Given,

Area of cross-section of the pump, A1 = 8 cm2 = 8 × 10–4 m2

Number of holes, n = 40

Radius of each hole, r = d/2 = 0.5 × 10–3 m

Area of cross-section of each hole, a = πr2 = π (0.5 × 10–3)2 m2

Total area of 40 holes, A2 = n × a = 40 × π (0.5 × 10–3)2 m2 = 31.41 × 10–6 m2

Speed of flow of liquid inside the tube, v1 = 1.5 m/min = 0.025 m/s

Let the speed of ejection of liquid through the holes is v2.

According to the equation of continuity, 

A1v1=A2v2v2=A1v1A2=8×10-4×0.02531.61×10-6

= 0.633 m/s