1. Chapter 11 – Forces in Fluids
Pressure = force/area
Examples of units for pressure:
newtons/m2 lbs/in2
Fluid (liquid or a gas) exerts pressure in all directions.
All the forces exerted by the individual molecules in a fluid add together to make up the total pressure of a fluid.

2. Atmospheric Pressure
Average atmospheric pressure at sea level = 10.1 N/cm2
In English units atmospheric pressure is lbs/in2
This is the weight of the column of air above us.
Air pressure decreases with elevation (ears pop).
Water pressure increases with depth

3. Pascal’s principle – When a force is applied to a confined fluid, an increase in pressure is transmitted equally to all parts of the fluid
Hydraulic system can multiply force

4. Buoyancy
Archimedes’s principle – the buoyant force of an object is equal to the weight of the water it displaces.
If the buoyant force is greater than the gravitational force (weight) on the object, the object will float.

5. Density = mass/volume
Density of water = 1g/cm3 = 1g/mL
If the density of an object is greater than one, it will sink. If the density of an object is less than one, it will float **in water**

8. Examples: airplane wing
Bernoulli’s Principle – The faster air moves over a surface the less pressure it exerts on the surface
Examples: airplane wing
Wind goes faster over the top of the wing (less pressure)

9. Examples: wind over a surface
Paper
Ground
**Less pressure on the top of the paper **

10. Examples: Atomizer
Air
Low pressure pulls liquid up
Liquid

11. Example: Ball in a vertical air stream
Less pressure on right pulls the ball back into air stream