Demos: 2B-04 Liquid Pressure
At any given point in a stationary liquid, the pressure forces are the same in all directions. A pillbox shaped sensor has a rubber diaphragm and is attached to a liquid manometer. The sensor is lowered into a deep vessel to a certain depth. The pressure at that depth is indicated on the manometer. The reading on the manometer does not change as the sensor is rotated.
Directions: The tube holding the sensor is held in place by a clamp that allows the tube to slide downward into the water. DO THIS VERY SLOWLY or you will find yourself drenched with red liquid from the manometer!!!. Once the sensor is at the desired depth, use the wire hook to rotate the sensor.
Suggestions for Presentation: It is often stated in texts that the pressure at a given depth is the same in all directions. Ask why this should be the case. Draw attention to the fact that what we are measuring here are forces. Pressure is not a vector--it has no direction associated with it. It is merely an indicator of how the forces are spread over a unit of area. If the liquid is in equilibrium, the forces acting at a point cannot have a preferential direction or the liquid would move.
Applications: None directly.