A water spray gun is attached to a hose of cross sectional area $30 \mathrm{~cm}^{2}$. The gun comprises of 10 perforations each of cross sectional area of $15 \mathrm{~mm}^{2}$. If the water flows in the hose with the speed of $50 \mathrm{~cm} / \mathrm{s}$, calculate the speed at which the water flows out from each perforation. (Neglect any edge effects)

(B) $10 \mathrm{~m} / \mathrm{s}$

(A) $100 \mathrm{~m} / \mathrm{s}$

(C) $1000 \mathrm{~m} / \mathrm{s}$

(D) $15 \times 10^{2} \mathrm{~m} / \mathrm{s}$

JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Fluid Mechanics

A water spray gun is attached to a hose of cross sectional area

30 cm^{2}

. The gun comprises of 10 perforations each of cross sectional area of

15 mm^{2}

. If the water flows in the hose with the speed of

50 cm / s

, calculate the speed at which the water flows out from each perforation. (Neglect any edge effects)

(A) $100 m / s$
(B) $10 m / s$ ✓ Correct
(C) $1000 m / s$
(D) $15 \times 1 0^{2} m / s$

Answer: (B)

Solution

By continuity the volume flow in the hose equals the total flow through the perforations:

A_{1} V_{1} = n a v

. With

A_{1} = 30 c m^{2}

V_{1} = 50 cm/s

n = 10

and

a = 15 m m^{2} = 0.15 c m^{2}

v = \frac{30 \times 50}{10 \times 0.15} = \frac{1500}{1.5} = 1000 cm/s

. Each jet leaves at

10 m/s

JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Single correct option

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