A horizontal pipe narrows from A₁ to A₂ < A₁. Compared to the wider section, in the narrower section the fluid:

1. By continuity, A₁v₁ = A₂v₂. With A₂ < A₁, v₂ > v₁ — the fluid speeds up. 2. Horizontal pipe: no change in height; Bernoulli becomes P + ½ρv² = const. 3. Larger v² ⇒ smaller P. So pressure DROPS in the narrow section. 4. This is the Venturi effect — also why an aerofoil generates lift. _Source: NCERT Class 11 Physics Ch 9 §9.6 (Bernoulli applications)_