Question

A long, horizontal hose of diameter 5.4 cm is connected to a faucet. At the other end, there is a nozzle of diameter 1.2 cm. Water squirts from the nozzle at velocity 20 m/sec. Assume that the water has no viscosity or other form of energy dissipation.

a) What is the velocity of the water in the hose?
b) What is the pressure differential between the water in the hose and water in the nozzle?
c) How long will it take to fill a tub of volume 120 liters with the hose?

Answer 1

a) 0.988 m/s

b) 199512 Pa

c) 57.52 s

Step-by-step explanation:

given that

A

A1 v1 = A2 v2

d1² v1 = d2² v2

v2 = [d1/d2]² v1

v2 = (1.2/5.4)² * 20

v2 = 0.049 * 20

v2 = 0.988 m/s

B

P + 1/2 ρ v² = K.

[p2 - p1] = 1/2 ρ [v1² - v2²]

[p2 - p1] = 1/2 * 1000 [20² - 0.988²]

[p2 - p1] = 500 * (400 - 0.976)

[p2 - p1] = 500 * 399

[p2 - p1] = 199512 Pa

C

Flow rate = AV = π [d²/ 4 ] * v

= π [0.012² / 4 ] * 20 = 0.00226 m³ /s

= π [0.054² / 4 ] * 0.988 = 0.00226 m³ /s

130 liters = 0.13 m³

t = 0.13/ 0.00226 = 57.52 s