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Science

Hydraulics

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Pressure can be transmitted through liquids. In hydraulic machines, exerting a small force over a small cross-sectional area can lead to pressure being transmitted, creating a large force over a large cross-sectional area. This ability to multiply the size of forces allows hydraulics to be used in many applications such as car-braking systems.

Pressure in liquids

Particles in liquids are close together, making liquids virtually incompressible [incompressible: Cannot be compressed.. As the particles move around, they collide with other particles and with the walls of the container. The pressure in a liquid is transmitted equally in all directions, so a force exerted at one point on a liquid will be transmitted to other points in the liquid.

Pressure is calculated using the equation:

An equation triangle showing pressure in liquids: F over P and A

where:

P = pressure in pascals, Pa

F = force in newtons, N

A = cross-sectional area in metres squared, m2

Worked example

A force of 250 N is exerted over an area of 10 m2. What is the pressure?

pressure

= force ÷ cross-sectional area

pressure

 

= 250 ÷ 10

= 25 Pa

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