3.3 Fluids

Liquids and gases are examples of fluids.

Particles in a fluid can move past each other.

Fluids exert pressure (push) evenly in all directions.

Pressure is the amount of force exerted on a given area surface.

When you add air to a tire, you are pushing air into the tire. Inside the tire, the air molecules push against each other and against the walls of the tire.

As you pump more air into the tire, the pressure inside the tire increases. Why?

The SI unit of pressure is the pascal.

You calculate pressure by dividing the force by the area over which the force acts.

Buoyant force is the upward force that keeps an object immersed in or floating on a fluid.

Archimedes' principle is used to find buoyant force. Archimedes' principle states "The buoyant force on an object in a fluid is an upward force equal to the weight of the fluid that the object displaces."

States that if the pressure in a container is increased at any point, the pressure increases at all points by the same amount.

Hydraulic devices use liquids to transmit pressure from one point to another.

Because these liquids cannot be compressed into a much smaller space, they can pass on pressure better than gases can.

Hydraulic devices can multiply forces.

Use books to look at Figure 5 (pg 92)

Fluids in motion have some properties in common.

Fluids move faster through small areas than through larger areas, if the overall flow rate remains the same.

But fluids also vary in the rate at which they flow.

Viscosity is a liquid's resistance to flow and it depends on the particles attracton.

The stronger the attraction between a liquid's particles, the more viscous the liquid is.

Example: Honey flows more slowly than lemonade because honey has a higher viscosity than lemonade.