1. Physics Section 8.2 Apply the properties of pressure
Fluids exert pressure on any object within the fluid. Pressure is the magnitude of the force on a surface per unit area.
P = F P = pressure (Pa)
A F = force (N)
A = area (m2)
The unit of pressure is the Pascal. (N/m2)

2. Pascal’s Law: Pressure applied to a fluid in a closed container is transmitted equally to every point in the fluid and to the walls of the container.
A small force F1 is applied to a small area A1 to create a large force F2 over a large area A2.

3. problem
In a hydraulic lift, a 620 N force is exerted on a .20 m2 piston in order to support a weight that is placed on a 2.0 m2 piston. How much pressure is exerted on the narrow piston? How much weight can the wide piston lift?

4. P = ρhg P = pressure (Pa) h = depth (m) ρ = density (kg/m3)
g = gravity acceleration
The pressure due to air at sea level is approximately 101,000 Pascals. Demo:Can crush/water boil

5. P = Po + ρgh P = absolute pressure
The gauge pressure of a fluid is the pressure generated by the fluid alone. The absolute pressure is the sum of the gauge pressure and the atmospheric pressure. The absolute pressure depends upon the depth.
P = Po + ρgh P = absolute pressure
Po = atmospheric pressure
= 1.01 x 105 N/m2
h = depth (m)
ρ = density (kg/m3)
g = gravity acceleration

6. problem
What is the gauge pressure at the bottom of a water tank that is 50 m tall?

7. The pressure at the top and bottom of a submerged box are different.
Net force on a submerged object Fnet = mf·g = ρgV This force is the buoyant force.

8. problem
A box with dimensions of .50 m by .35 m by .20 m is submerged in water. Find the net buoyant force on the box.

9. Assignment
Page 283
Problems 1 – 4