Hydraulic & Pneumatic SystemsProperties of Fluids

Properties of FluidsFluid: A substance that flows and takes the

shape of its container. They also cannot form any shapes themselves.

i.e: Water and air are fluids, sand and sugar are not.

The study of fluids is divided into two branches:Hydraulics: The science behind the mechanical

properties of liquids.Pneumatics: The science behind the mechanical

properties of gases.

Systems & Our Bodies

Our bodies contain natural pneumatic & hydraulic systems:

Hydraulic system: Circulatory system, blood is circulated throughout the body.

Pneumatic system: Respiratory system, air is brought in and out of the lungs.

Kinetic Molecular Theory

Before we look at specific fluid properties, we re-examine the kinetic molecular theory which states:

1. All substances are made up of identical molecules.

2. The particles are in constant motion. Solids move the slowest -> Gases move the

fastest

3. Particles have spaces in-between them. Solids have smallest space -> Gases have

most space.

Solid Liquid Gas

DensityDefined as the mass per unit volume.

Given by:

Eg.1: A substance has a mass of 150g and a density of 4.5 kg/m3, what volume does it occupy?

V

mD

WhereD = density (kg / m3)m = mass (kg)V = volume (m3)

CompressibilityThe ability of a substance to be pressed

closer together.

Gases are more compressible than liquids. Why?

Particle theory of matter states spaces between gases are larger than liquids.

These spaces can be shrunk.