Verified Solution • 2025–26 Session
moderate
Q9.15: NCERT Physics - Part 2 MECHANICAL PROPERTIES OF FLUIDS 9.15 Solution: Figures 9.20(a) and (b) refer to the steady flow of a…
⚠️ Common Exam Traps & Conceptual Pitfalls
Students often assume a higher liquid level means higher pressure, but in a flowing fluid Bernoulli’s equation shows $p+ frac12 ho v^2$ is constant. Thus where the cross‑section is smaller and $v$ is larger, the static pressure $p$ must be lower, so the fluid level should be lower—not higher—at the constriction. Avoid equating height with pressure in a moving fluid.
Figures 9.20(a) and (b) refer to the steady flow of a (non-viscous) liquid. Which of the two figures is incorrect? Why?
Step-by-Step Verified Solution
**Answer:** Figure (a) is incorrect.
**Step-by-Step Explanation:**
By the equation of continuity, where the area is smaller, the velocity is larger. By Bernoulli's principle, where velocity is larger, pressure is smaller. In figure (a), the liquid level in the tube at the constriction is higher, indicating higher pressure where velocity should be higher (and pressure lower). This violates Bernoulli's principle. Hence, (a) is incorrect.
All Questions in this Chapter
Related Learning Resources & Exam Preparation
Chapter Practice Bank
Practice all topic-wise questions from MECHANICAL PROPERTIES OF FLUIDS
Reference Textbook Solutions
Explore complete chapter exercises for NCERT Physics - Part 2
Competitive PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring