Ch 14 - Hydraulics

Hydraulic Devices

•If there are no outside forces (like gravity) acting on a fluid, the pressure exerted by the fluid will be the same throughout, and in all direction.

•This fact allows hydraulic devices to work.

Try pushing a stopper

into a bottle full of water

What happens?

The pressure

applied to the water

by the stopper

acts equally in all

directions, including

up!

Hydraulic Devices

•produce enormous forces with the application of only a very small force

•hydraulic devices multiply forces

•example = hydraulic brakes on a car

Allows us to lift and rotate people without effort

or stop cars just by pushing a brake pedal

How it Works:

1. A small force is applied to the smaller piston.

#1

2. The pressure created by the force pushes against

the liquid.

#2

3. The piston moves a large distance as it presses on the

liquid.

#3

4. The pressure is transmitted equally

throughout the liquid.

#4

5. The transmitted pressure pushes upward against the

larger piston, but over a smaller distance.

#5

6. The pressure on every square cm of the larger piston

is equal to the pressure on every square cm.

#6

7. Since the # of square cm (or area) is greater on the larger piston, the force is

greater.

#7

Some animals use hydraulics in order to move.

These animals have fluid filled bodies which allow them to use hydraulics.

Things to Remember• The pressure is equal in each piston.

• Force is calculated by multiplying the pressure times the area.• There is a direct ratio between the area of one piston & the length of the movement of the other piston.