JEE Main 2026 Apr 8 Shift 2, Physics Q8: Hydrodynamic

JEE Main2026Apr 8, Shift 2Physics

A liquid of density $600$ kg/m $^{3}$ flowing steadily in a tube of varying cross-section. The cross-section at a point $A$ is $1.0$ cm $^{2}$ and that at $B$ is $20$ mm $^{2}$ . Both the points $A$ and $B$ are in same horizontal plane, the speed of the liquid at $A$ is $10$ cm/s. The difference is pressures at $A$ and $B$ points is _________ Pa.

A
$18$
B
$144$
C
$36$
D
$72$

Solution

Velocity at B from continuity, with areas $A_{1} = 1.0 cm^{2} = 100$ mm $^{2}$ and $A_{2} = 20$ mm $^{2}$ :

$A_{1} v_{1} = A_{2} v_{2} ⟹ v_{2} = \frac{100}{20} \times 10 = 50$ cm/s.

Convert to SI: $v_{1} = 0.10$ m/s, $v_{2} = 0.50$ m/s.

Bernoulli (horizontal flow, no height term): $P_{1} - P_{2} = \frac{1}{2} ρ (v_{2}^{2} - v_{1}^{2})$ .

$= \frac{1}{2} (600) (0.25 - 0.01) = 300 \times 0.24 = 72$ Pa.

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JEE Main 2026 Apr 8 Shift 2, Physics Q8: Hydrodynamic

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