What effect does narrowing the air path have on airspeed?

• A. Air slows down
• B. No effect
• C. Air speeds up
• D. Airspeed depends on altitude

Answer: (C)

Narrowing the air path causes the air to flow faster through the restricted section. This follows the continuity principle: the same amount of air must pass through each cross-section per unit time, so reducing the cross-sectional area increases velocity. In effect, squeezing the air through a smaller space makes it speed up, similar to a Venturi nozzle where increased velocity comes with a drop in static pressure. Altitude or density changes don’t negate this local acceleration; they mainly affect how much air is available overall, not the fact that a smaller opening speeds up the flow. Therefore, the air speeds up.