1. Fluid Pressure

2. Liquid Pressure
The pressure a system of particles (solid, liquid, or gas) puts on any object is the total force of the system divided by the area
Pressure = Force / Area
𝑃= 𝐹 𝐴
The units of pressure is the Pascal = Pa
Please remember the units!!

3. Liquid Pressure Pressure on the Earth varies as a function of height
When your ears pop, it means they are adjusting to a new pressure
The pressure of the Earth's atmosphere at sea level is 100,000 Pa

4. Liquid Pressure
The deeper you go into a fluid, the more pressure you feel.
Blaise Pascal, a French Physician, discovered that the shape of a container had no effect on the pressure at any given depth.

5. Liquid Pressure
In a hydraulic system, fluid is confined to two chambers. Each chamber has a piston that is free to move.
You put a force F1 on a piston with area A1, and that will exert a pressure in the fluid that transmits to the other piston, exerting F2 on area A2

6. Liquid Pressure So if P1 = F1/A1, P2 = F2/A2, and P1 = P2 then:
𝐹 1 𝐴 1 = 𝐹 2 𝐴 2
The fluid connecting the pistons is the link. This is how car brakes work.

7. Liquid Pressure The pressure due to a liquid is calculated as
Pressure = density of fluid x gravity x height
𝑃= 𝜌𝑔ℎ
ρ = is pronounced (rho) and is a greek letter used for density

8. Liquid Pressure
Try these problems… go on…. no pressure 

9. Liquid Pressure Suppose we put an object in a fluid of height l.
The buoyant force is defined as the upward force on an object within a fluid
Remember, if the density of the fluid is greater than the object, the object will float. If opposite, it will sink.

10. Example: A dumb teenager is floating in a freshwater lake, where just his head is sticking above the water. His weight is 640N. Calculate the volume of his body that is submerged in the lake. The density of water is 1000kg/m³.
P = F/A -> F = PA = ρghA = ρVg
640N = 1000kg/m^3 * V * 10m/s^2
V = 640 / (1000 * 10) = m^3