The top surface of a calm, smoothly flowing stream is always at atmospheric pressure. As water in this stream suddenly speeds up, the water's top surface
A) shifts upward slightly above the normal stream level.
B) shifts downward slightly below the normal stream level.
C) stays at the same height and does not begin to rotate.
D) stays at the same height but begins to rotate clockwise as viewed from above.

Question

Quizplus · Accepted Answer

According to Bernoulli's principle, as the speed of a fluid increases, its pressure decreases. Therefore, if water in a stream suddenly speeds up, the pressure at the top surface decreases, causing the water level to drop slightly below the normal stream level.

The Top Surface of a Calm, Smoothly Flowing Stream Is