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

This means that liquids can be used to send forces from one place to another in hydraulic systems Liquids cannot be compressed because the particles are already close together

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 http://hyperphysics.phy-astr.gsu.edu/Hbase/pasc4.html#c1 http://phschool.com/atschool/phsciexp/active_art/hydraulic_system/index.html

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 http://hyperphysics.phy-astr.gsu.edu/Hbase/pasc.html#hpcal

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 f p a Force = 20N Force = 10N Y Area = 10cm2 X Ask pupils to calculate the pressure from piston x. Demonstrate how to calculate the force by rearranging the equation (higher pupils will probably only understand this point) Area = 10cm2 pressure = force Area = 40cm2 area

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: In order for pressure to be transmitted in a fluid, the fluid must be confined. If the hydraulic system is leaking, the fluid is not confined. In order for pressure to be transmitted in a fluid, the fluid must be confined. If the hydraulic system is leaking, 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 Examples: Bus ramps Bus doors Dentist drill Nail gun Lungs Scuba gear Video