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 in pressures at A and B points is Pa.

Physics · Fluid Mechanics

JEE Main 2026 — 8 April, Evening Shift — Question 8

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

Option A:
18
Option B:
144
Option C:
36
Option D:
72
Correct

Answer: D

Step-by-step solution

Continuity: $A_1v_1 = A_2v_2$ ⇒ $1\times10 = (20/100)\times v_2$ ⇒ $v_2 = 50$ cm/s. Bernoulli: $P_1 - P_2 = \frac12\rho(v_2^2 - v_1^2) = 0.5\times600\times(2500-100)\times10^{-4} = 72$ Pa.

Answer key and solution verified before publishing.

Practise Fluid Mechanics

Start with this question, then two more from the same chapter — with a tutor that explains every step. Free.

Solve a similar one free

Exam: JEE Main 2026
Paper: 8 April, Evening Shift
Subject: Physics
Chapter: Fluid Mechanics
Topic: Bernoulli's Equation and its Applications