I have encountered this question in my Giancoli Physics textbook, and I am pretty convinced that the answer should be A and E. But the solutions manual has neglected E as a potential answer and focused solely on A. Can someone point out what am I missing out? Perhaps a linguistic trick?

Water flows in a horizontal pipe that is narrow but then widens and the speed of the water becomes less. The pressure in the water moving in the pipe is

(a) greater in the wide part.

(b) greater in the narrow part.

(c) the same in both parts.

(d) greater where the speed is higher.

(e) greater where the speed is lower.

Textbooks Answer: enter image description here


1 Answer 1


For this problem the wider part and lower velocity region is the same thing. So I would expect (e) to also be correct (unless there is a sketch that complicates the problem)

What you have to realize however, is that Bernoulli's equation is ignoring viscous effect (friction), so pressure and velocity are not related. What matters is a pressure drop, otherwise you would not have any flow at all. If the wider pipe is long enough, the pressure there will after some distance be smaller than the pressure in the narrow pipe.

  • 1
    $\begingroup$ Makes sense, thank you $\endgroup$
    – Doe Pual
    Jan 23, 2022 at 16:52

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