Some applications of
Reminders and uses:
Hydraulic machines use liquid fluid power
to perform light or heavy work in many situations.
vehicles are a common examples (illustrated below).
In these machines, hydraulic fluid is
pumped to various hydraulic motors and hydraulic cylinders throughout the
machine and becomes pressurized sufficiently to overcome resistance and
The fluid is controlled directly or
automatically by control valves and distributed through tubes/pipes.
Hydraulic systems, like pneumatic
systems, are based on the fact that any pressure applied to a fluid inside a
closed system will transmit that pressure equally everywhere and in all
To be effective in transmitting
force, hydraulic systems must use an in-compressible liquid as its
fluid, rather than a compressible gas.
The wide-spread use of hydraulic machinery is because large amounts of
power that can be transferred mechanically, and relatively simply,
through small tubes and flexible hoses to achieve movement e.g. lifting
(1) Hydraulic jack system
for lifting vehicles in garages
Four hydraulic piston and cylinder systems are used to jack up the red van. The
fluid can be oil or compressed air.
The Land Rover (left) and the red van (right) both have
Key for the 5 photographic diagrams:
suspension spring; H = the pipe conveying the hydraulic brake fluid
D = the brake drum and disc on which the brake pads in
casing P are forced into contact with the smooth disc by the hydraulic
transmitted force when you press the brake pedal.
A conveys speed of rotation information for the correct
functioning of the advanced ABS braking
How does the hydraulic brake system of a motor vehicle work?
When you press on the brake pedal of motor vehicle, the force is
transmitted through the brake fluid liquid by a pipe system (in modern cars it
is aided by an electric pump system).
The braking mechanism involves several
pistons and cylinders, known as the master cylinder (activated by the pedal) and
slave cylinders on the brake drums (4 of the latter in the case of 4 wheeled
The transmitted force pushes the brake pads onto the brake disc on
the brake drum and the resulting friction reduces the speed of the vehicle.
you take you foot off the brake pedal, the force is no longer transmitted and
springs move the brake pads away from the brake discs to avoid unnecessary
'Hydraulic' photographs by courtesy of Mark Raw of M T R
Autotech Ltd garage, Castleton, North Yorkshire, England
(2) Plant machinery - examples of
using hydraulic machinery
A huge range of excavators
('diggers'), diggers, bulldozers, elevated work platforms are used on demolition sites,
construction sites use liquid power in hydraulic systems.
In the above photographs you can see
the shiny steel systems of the hydraulic systems.
Index physics Forces notes 6. Forces & pressure in
Keywords, phrases and learning objectives for forces involving
Be able to describe and explain applications and uses of hydraulic systems
up cars, plant machinery like diggers and bulldozers, elevated platforms
Know that hydraulic systems work by the transmission of force
through a liquid to create pressure, or applying pressure to produce
an applied force in machines.
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Index physics Forces notes 6. Forces & pressure in fluids, calculations