Final answer:
The level of water should be above the stem of an inverted funnel in a hydraulic experiment to ensure consistent atmospheric pressure for accurate hydraulic principle demonstrations and measurements.
Step-by-step explanation:
In a hydraulic experiment, the level of water should be above the level of the stem of an inverted funnel to ensure consistent atmospheric pressure is applied at the surface of the water inside and outside of the funnel. This uniform pressure is crucial because it enables the comparison of other pressures or the verification of various hydraulic principles without the complication of differing atmospheric pressures.
For example, in the situation with a manometer, the fluid reaches equal levels on either side when both sides are open to the atmosphere because atmospheric pressure is the same at the surface of both sides, regardless of the tube diameters. Similarly, Pascal's Principle and Hydraulics describe how the pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel, which is only valid if the atmospheric pressure is consistent. Therefore, the water in the experiment must cover the funnel's stem to maintain equal atmospheric pressure and enable accurate hydraulic principles demonstrations and measurements.