Pressure difference from height variation in U-tube

Steps:

• Determine height difference Δh between levels P and Q from diagram (0.04 m).
• Apply formula ΔP = ρ g Δh, with ρ = 2000 kg/m³ and g = 9.8 m/s².
• Compute ΔP = 2000 × 9.8 × 0.04 = 784 Pa (≈780 Pa).
• Result gives pressure difference of 780 Pa.

Why A is correct:

• ΔP = ρ g Δh directly yields 780 Pa using hydrostatic pressure formula and diagram heights.

Why the others are wrong:

• B: Overestimates by using g ≈ 10 m/s² without adjusting height precisely.
• C: Assumes double the height difference (e.g., 0.08 m).
• D: Ignores height, using only ρ g (as if h = 1 m).

Final answer: A