The arrangement shown in the figure measures the velocity

The arrangement shown in the figure measures the velocity V of a gas of density 1 kg/m³ flowing through a pipe. The acceleration due to gravity is 9.81 m/s². If the manometric fluid is water (density 1000 kg/m³) and the velocity V is 20 m/ s, the differential head h(in mm) between the two arms of the manometer is _________.

1. h = 30.31 mm of water
2. h = 10.12 mm of water
3. h = 14.38 mm of water
4. h = 20.38 mm of water

Dynamic pressure of gas = (δgh)_water

1	δ_gasv₂ = δ_m × 9.81 × h
2

1	× 1 × (20)² = 1000 × 9.81 × h
2

h = 0.02038 m of water
h = 20.38 mm of water