- Pressure is the force per unit area on a surface.
- Fluid pressure results from the motion of the atoms or molecules that make up the fluid.
- Pressure at a given level in a fluid is the same in all directions. Pressure decreases with altitude and increases with depth.
Transmitting Pressure in a Fluid
- According to Pascal's principle, an increase in pressure on a confined fluid is transmitted equally to all parts of the fluid.
- A hydraulic device works by transmitting an increase in pressure from one part of a confined fluid to the other. A small force exerted over a small area at one place results in a large force exerted by a larger area at another place.
- The upward force on a object submerged in a fluid is called the buoyant force.
- The buoyant force on an object is equal to the weight of the fluid displaced by the object. This is Archimedes' principle.
- An object will sink, rise to the surface, or stay where it is a fluid depending on whether its density is less then, greater than, or equal to the density of the fluid.
Applying Bernoulli's Principle
- The pressure in a fluid decreases as the speed of the fluid increases. This is Bernoulli's principle.