2B20.3 Pascal's Vases Tubes of various shapes are joined at the bottom. Filled with water, the level will reach the same height in all tubes. A fifty pound weight is lifted when a cylinder with a piston is evacuated. A solid cylinder fits snugly inside a larger pail, and the two are balanced by an equal mass on the other side of a scale. The cylinder is then suspended below the pail and lowered into water, making the scale tip toward the other mass.
Balance is restored by pouring the water displaced by the cylinder into the pail.
Pressing on the rubber top of the tube increases the pressure throughout, forcing more water into the diver, changing its buoyant force and causing it to sink. A diver floats in a soda bottle completely filled with water. Since the water is incompressible, squeezing on the bottle causes very little volume change but drives the diver straight to the bottom. 2B40.4 Weight of Air An evacuated flask is balanced on a scale, and then air is allowed back into it. A long, helical pipe is tilted 45 degrees and the lower end is inserted in water.