Gravity causes fluid molecules to press on molecules below {pressure, fluid} {fluid pressure}|. Deeper molecules have more pressure, because more molecules are above them. Pressure P, force F per area A, at point below fluid surface is density d times depth h times gravity acceleration g: P = F / A = (m * g) * (h / V) = (m / V) * g * h = d * g * h. Pressure is directly proportional to gravity acceleration, because acceleration times mass is force. Pressure is directly proportional to density, because density relates to molecule mass. Pressure is directly proportional to depth, because depth relates to molecule number. Pressure does not depend on total surface area, because pressure is force per unit area.
fluid level
Liquids rise to equal heights at all openings to atmosphere, because pressures and potential energies are equal at liquid surfaces.
cause
Random molecule motions cause fluid pressure. Random motion exerts force and pressure equally in all directions, even upward or at angle. Container wall slope has no effect. Pressure is the same at all points at same depth. The net effect of random motions is that pressure is perpendicular to fluid surface, because random motions are symmetric around perpendicular.
temperature
Temperature increase increases fluid pressure, because molecules move faster.
density
More and/or heavier molecules have higher density and exert more pressure.
gas
Gas has random translational kinetic energy per unit volume, making force per unit area on container walls. Random translational kinetic energy depends on mass and molecule average velocity. If volume decreases, pressure goes up. If temperature decreases, pressure goes down. If pressure decreases, volume goes up. If pressure increases, temperature goes up.
Physical Sciences>Physics>Dynamics>Fluid>Pressure
5-Physics-Dynamics-Fluid-Pressure
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Date Modified: 2022.0224