Pressure equivalence and hydrostatic head:\n1 kgf/cm^2 (kilogram-force per square centimetre) is approximately equal to which of the following?

Introduction / Context:
Engineers frequently convert among distinct pressure units: kgf/cm^2, bar, kPa, psi, and hydrostatic head in metres of water (m H2O). Correct conversions are vital for sizing pumps, checking instrument ranges, and reading legacy plant data.

Given Data / Assumptions:

• 1 kgf/cm^2 ≈ 0.9807 bar ≈ 98.07 kPa.
• Hydrostatic head of 10 m water at 4°C corresponds to ≈ 0.98 bar (density ~1000 kg/m^3, g ≈ 9.81 m/s^2).
• 1 atm ≈ 760 torr ≈ 1.01325 bar; 1 kPa is much smaller than 1 bar.

Concept / Approach:
Hydrostatic pressure P for a liquid column is P = rho * g * h. For water, rho*g ≈ 9810 Pa/m, hence 10 m water column ≈ 98.1 kPa ≈ 0.981 bar. Matching this to 1 kgf/cm^2 (≈ 98.1 kPa) confirms the conversion. This shows why older gauges labeled “kg/cm^2” align closely with “bar.”

Step-by-Step Solution:
Compute 1 kgf/cm^2 in SI: 1 kgf = 9.81 N; 1 cm^2 = 1e-4 m^2; so 1 kgf/cm^2 ≈ 9.81 / 1e-4 = 98,100 Pa = 98.1 kPa.Relate to water head: 98.1 kPa / (ρg) ≈ 98,100 / 9810 ≈ 10 m.Therefore 1 kgf/cm^2 ≈ 10 m of water column.

Verification / Alternative check:
Compare to atmospheres: 1 atm is 101.325 kPa, which corresponds to about 10.33 m of water—slightly higher than 10 m, mirroring the small difference between 1 kgf/cm^2 and 1 atm.

Why Other Options Are Wrong:
760 torr corresponds to 1 atm, not 1 kgf/cm^2 (which is ~0.96 atm).1 kPa is far smaller; 1 kgf/cm^2 is ~98 kPa.1 m of water column is only ~9.81 kPa, one-tenth of the correct value.

Common Pitfalls:
Confusing kgf/cm^2 (force-based unit) with kg/cm^2 (mass per area); neglecting the slight differences between 1 bar, 1 atm, and 1 kgf/cm^2.

Final Answer:
10 metres of water column