What is the depth of a point below water surface in sea where pressure intensity is 1·006 MN/m² and the specific gravity of seawater is 1·025?
- A70 m
- B80 m
- C90 m
- D100 mCorrect
Solution
Concept
Hydrostatic pressure
Formula
p = ρ g h
Step-by-step solution
1. ρ = 1.025 × 1000 = 1025 kg/m³. 2. h = p / (ρ g) = 1.006 × 10⁶ / (1025 × 9.81) = 100.05 m ≈ 100 m.
Explanation
The gauge pressure in a liquid grows linearly with depth.
Why the other options are wrong
70, 80 and 90 m would give pressures of 0.70, 0.80 and 0.90 MN/m².
Shortcut
h = p/γ.
Common mistake
Using the density of fresh water (gives 102.5 m).
Correct answer: D) 100 m