Verified Solution • 2025–26 Session moderate

Q9.10: NCERT Physics - Part 2 MECHANICAL PROPERTIES OF FLUIDS 9.10 Solution: In the previous problem, if 15.0 cm of water and spirit each…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students frequently calculate the pressure difference using only the newly poured 15.0 cm of liquid, ignoring the initial 10.0 cm and 12.5 cm heights already present in the arms. You must use the total cumulative heights (25.0 cm for water and 27.5 cm for spirit) in the hydrostatic balance equation to find the correct mercury level difference.

In the previous problem, if 15.0 cm of water and spirit each are further poured into the respective arms of the tube, what is the difference in the levels of mercury in the two arms? (Specific gravity of mercury = 13.6)

Step-by-Step Verified Solution

**Answer:** 0.22 cm **Step-by-Step Explanation:** Initial heights: water = 10.0 cm, spirit = 12.5 cm. After pouring: water = 25.0 cm, spirit = 27.5 cm. Pressure balance at mercury level:
ρwghw=ρsghs+ρHggΔh\rho_w g h_w = \rho_s g h_s + \rho_{Hg} g \Delta h
1×25.0=0.8×27.5+13.6×Δh1 \times 25.0 = 0.8 \times 27.5 + 13.6 \times \Delta h
25.0=22.0+13.6Δh25.0 = 22.0 + 13.6 \Delta h
Δh=3.013.6=0.22 cm\Delta h = \frac{3.0}{13.6} = 0.22 \text{ cm}

All Questions in this Chapter

Q9.1 Q9.2 Q9.3 Q9.4 Q9.5 Q9.6 Q9.7 Q9.8 Q9.9 Q9.10 Q9.11 Q9.12 Q9.13 Q9.14 Q9.15 Q9.16 Q9.17 Q9.18 Q9.19 Q9.20

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