Fluid Pressure

Fluid Pressure What’s a fluid?

Fluid: anything that flows

Fluid: anything that flows ???

like Liquids

and Gases

Pressure Notes (Continued) Fluids: anything that flows (liquid or gas)

PAUSE Q: Why should we care about fluid pressure?

PAUSE Q: Why should we care about fluid pressure? A: Air, weather, swimming, diving, dish washers, tires, heavy machinery, and our bodies all depend on fluid pressure.

What does fluid pressure depend on? Question: What does fluid pressure depend on?

Let’s Find Out Imagine a diver trying to swim to the bottom of the ocean.

Let’s Use the Equation for Pressure Imagine a diver trying to swim to the bottom of the ocean.

What is the force on the diver?

The force on the diver is from gravity pushing on the water above the diver.

Remember The force on the diver is from gravity pushing on the water above the diver.

The force on the diver is from gravity pushing on the water above the diver. So

but… What is m?

m is the mass of the water above the diver.

Let’s Use Density to Find m m is the mass of the water above the diver.

Let’s Use Density to Find m

We need to find an equation for m

We need to find an equation for m multiply both sides by V

We need to find an equation for m cancel out

We need to find an equation for m rewrite

We found an equation for m

Plug in our equation for m m is the mass of the water above the diver.

Now

but… What is V?

V is the volume of water above the diver.

V is the volume of water above the diver. height (h) Area (A)

Now V is the volume of water above the diver.

Reduce V is the volume of water above the diver.

Finally

Question (Answered): Q: What does fluid pressure depend on? A: Since P = ρhg, pressure only depends on density and height.

Your Turn Find the pressure at the bottom of the ocean. The density of water is 1 g/cm3. The ocean is about 10,000m deep.