Flow velocities in an incompressible fluid can be measured with which one of the following?

Flow velocities in an incompressible fluid are measured using a Venturi tube, which operates on Bernoulli's principle [c1][t7]. As fluid passes through the tube's constricted throat, its velocity increases while its pressure decreases [t2][t5]. By measuring this pressure difference, typically with a manometer, the flow velocity or discharge rate can be calculated [t1][t5]. In contrast, a barometer is specifically designed to measure atmospheric pressure [c2][c3]. A manometer is a general device for measuring fluid pressure differences rather than velocity directly, though it is often used as a component of a Venturi system [t2][t3]. A strain gauge measures the mechanical deformation or stress of an object rather than fluid flow [t1]. Therefore, the Venturi tube is the primary instrument among the options for determining flow velocity [t7][t8].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > Vapour Pressure of Water And Rate of Evaporation > p. 358
2. [2] Exploring Society:India and Beyond ,Social Science-Class VII . NCERT(Revised ed 2025) > Chapter 2: Understanding the Weather > THINK ABOUT IT > p. 35
3. [3] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 13: Weather > The Elements of Weather and Climate > p. 116