Q 11-09-028JEE MainJEE Main 2026 (8 Apr, Shift 2)Medium
A liquid of density $600\ \text{kg/m}^3$ flowing steadily in a tube of varying cross-section. The cross-section at a point $A$ is $1.0\ \text{cm}^2$ and that at $B$ is $20\ \text{mm}^2$. Both the points $A$ and $B$ are in same horizontal plane, the speed of the liquid at $A$ is $10\ \text{cm/s}$. The difference in pressures at $A$ and $B$ points is ______ Pa.
Answer: (D) $72$
Continuity: $A_Av_A = A_Bv_B$ with $A_A = 100\ \text{mm}^2$:
$v_B = \dfrac{100}{20} \times 0.1 = 0.5$ m/s.
Bernoulli (same height):
$$p_A - p_B = \frac{1}{2}\rho(v_B^2 - v_A^2) = \frac{1}{2} \times 600 \times (0.25 - 0.01) = 72\ \text{Pa}$$
Solution by Sreeraj P, M.Sc Physics