A spinning top has angular momentum that creates a force that keeps it from falling over, and it precesses. Mass in motion has momentum and/or angular momentum. That made me wonder: Does fluid in motion create angular momentum? If so, how would it materialize? Consider a fictional example: Let’s say a river has a cross-sectional area of 1000 square metres and is flowing at 1 metre per second. In 1 second, the amount of water flowing through the cross section at a particular point would be 1000 cubic metres. That corresponds to 1,000,000 kilograms. Basically, a mass is flowing past a point at the rate of 1,000,000 kilograms per second. Would this mass in motion create a force that can be measured? For example, on a bridge above the river, would the period of a pendulum indicate that gravity is decreased (or increased) as opposed to a time when the water is still, but still the same volume of water in the test volume? At this point, I am not concerned about quantitative information; I just want to know if a force materializes by a moving fluid or not.