When an object is immersed in liquid, the depth of the upper and lower surfaces is different, the depth of the lower surface is greater than that of the upper surface, and the pressure of the lower surface is greater than that of the upper surface. Therefore, the upward pressure generated by the liquid on the object is not equal to the downward pressure, so the object will act vertically upward, which is buoyancy. For an object immersed in a liquid, buoyancy is equal to the gravity that displaces the liquid, which is Archimedes principle; Its mathematical expression is f float = ρ gV drainage,

This principle applies to the buoyancy of objects in liquids as well as gases.

So, the answer is: vertically upward; It replaces the gravity of liquid; F float = gV discharges ρ liquid; Liquid; Gas.