Fluids & Pressure |

Fluids are any substance that can **flow.** So when we talk of states of matter

there are two of them that are fluids, liquids and gases.

there are two of them that are fluids, liquids and gases.

Any fluid will produce **pressure** because the particles that they are made of are in

motion and hitting the edges of the container. In the graphic below you can see

one particle bouncing around, when it hits the edge it pushes on it. Now if there

are billions of particles hitting it will produce more pressure.

motion and hitting the edges of the container. In the graphic below you can see

one particle bouncing around, when it hits the edge it pushes on it. Now if there

are billions of particles hitting it will produce more pressure.

standard terms we might use pounds per square inch, such as in the pressure of a

bicycle tire, but in metrics (SI) we use Newtons per square meters. (N / M ). One

Newton over one square meter is called a

so usually we measure pressure in a Kilopascal (KPa). This doesn't mean we

want to go around killing Pascal, it means 1000 Pascals.

2

Blaise Pascal was a great

scientist/mathematician/philosopher who discovered one

of the basic principles of fluid pressure so it is called

**Pascal's principle. **It says that when there is an

increase in pressure at any point in a confined fluid,

there is an equal increase at every other point in the

container. Unlike a solid, when you push on it the force

goes straight through to the other side, in a fluid the

force goes equally in all directions.

Think of a balloon, if you push down on the top it will

start pushing out on the sides too. This also explains

why a bubble is round, the air inside is pushing equally in

all direcftions.

scientist/mathematician/philosopher who discovered one

of the basic principles of fluid pressure so it is called

increase in pressure at any point in a confined fluid,

there is an equal increase at every other point in the

container. Unlike a solid, when you push on it the force

goes straight through to the other side, in a fluid the

force goes equally in all directions.

Think of a balloon, if you push down on the top it will

start pushing out on the sides too. This also explains

why a bubble is round, the air inside is pushing equally in

all direcftions.

Remember we said that a gas does not have a definite shape **or **

volume because the molecules are spread apart and in motion. If

you squeeze the gas into a smaller volume, the pressure will

increase. Notice in the graphic to the left, when the space gets

smaller the particles hit the walls more often. This is a basic rule

of gases, if you decrease the volume you will increase the pressure.

volume

you squeeze the gas into a smaller volume, the pressure will

increase. Notice in the graphic to the left, when the space gets

smaller the particles hit the walls more often. This is a basic rule

of gases, if you decrease the volume you will increase the pressure.