The total pressure at that point, however, is the pressure of the water plus the pressure of the air above the water. The cross-sectional area of the small piston is 0.0500 m 2 . What is the magnitude...The total pressure at that point, however, is the pressure of the water plus the pressure of the air above the water. The cross-sectional area of the small piston is 0.0500 m 2 . What is the magnitude of the weight than can be lifted by the large piston, which has a cross-sectional area of 0.100 m 2 ?