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A horizontal pipe narrows from A₁ to A₂ < A₁. Compared to the wider section, in the narrower section the fluid:
ASpeeds up; pressure drops
BSpeeds up; pressure rises
CSlows down; pressure drops
DSlows down; pressure rises
Answer & Solution
Correct answer: A. Speeds up; pressure drops
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)_
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