Chapter 9 :Hydraulics and Pneumatics

What we will learn this chapter

Hydraulic systems are systems that use a liquid under pressure to transmit a force and do work.

Liquids cannot be compressed because

the particles are already close together

Liquids cannot be compressed because

the particles are already close

together

This means that liquids can be used to send

forces from one place to another in hydraulic

systems

Liquids and Compression

Liquids CANNOT be compressed by ordinary means.

When pressure is applied to liquid in a pipe , the force can be transmitted over a distance.

Example: A long hose is connected to a water tap from the side of a building. Pressure is transmitted along the hose and forces the water out the other end of the hose.

Using Pascal´s Principle

Hydraulic devices

Hydraulic systems

Use liquids to transmit pressure in a confined fluid

A hydraulic system multiplies force by applying the force to a small surface area. The increase in pressure is then transmitted to another part of the confined fluid, which pushes on a larger surface area

Basic Hydraulic System 1) a pump, which creates

pressure for the system, and

2) a rotor or cylinder, which transfers the hydraulic energy back into mechanical energy in the form of rotary or linear

motion.

Hydraulic systems

Force = 10N

X Y

Area = 10cm2

Force = 20N

Area = 40cm2

pressure = area

force

Examples

Car brakes Dump truck lift Hydraulic lifts: raise cars off the ground Video

Why is a leak in a hydraulic system a problem?

Answer: Answer: In order for pressure to be transmitted in a fluid, the fluid must be confined. If the hydraulic system is If the hydraulic system is leaking, the fluid is not confinedleaking, the fluid is not confined.

Hydraulic brakes The brake system multiplies the force,

so a person can stop a large car with only a light push on the brake pedal

Pneumatic Systems

Pneumatic system: a system that uses a gas, usually air, under pressure to transmit a

force.

In order for a gas to be put to work in a fluid system, it must be compressed

ExamplesExamples:

Bus ramps

Bus doors

Dentist drill

Nail gun

Lungs

Scuba gear

Video