What happens when the pipe narrows?

Water flows steadily through a pipe. At one section the cross-sectional area is 6 cm² and the mean speed is 1.5 m/s. Farther along, the area is 2 cm².

What is the mean speed at the narrower section?

Organize the givens & assumptions

A1 = 6 cm²
A2 = 2 cm²
v1 = 1.5 m/s

Incompressible steady flow, no leaks or branches. Use section-averaged speeds.

A $4.5\ \mathrm{m\,s^{-1}}$
B $0.5\ \mathrm{m\,s^{-1}}$
C $1.5\ \mathrm{m\,s^{-1}}$
D $13.5\ \mathrm{m\,s^{-1}}$

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