1. and the use of liquid pressure
Hydraulics
and the use of liquid pressure

2. The important features of pressure in liquids
Liquids will transmit pressure throughout the liquid, regardless of the shape of the container
A force therefore can be applied wherever you want it
The force can be multiplied according the the area of the pistons used to push down on the water

3. Examples of the use of hydraulics
Car brakes
Car jacks
Fork lift trucks
Lifts
bulldozers
Television cameras

4. How car brakes use hydraulics
A small force on the brake pedal will act on a piston with a small area
The small piston pushes against the brake fluid
The pressure exerted is transmitted to all parts of the liquid
The pressure acts against four bigger pistons with larger areas
The large pistons will multiple the force and cause the brake pads to push against the wheels
As pressure is transmitted equally throughout the liquid, each brake works evenly too

5. Hydraulic brake
The diagram shows a simple brake where a pedal will push down on the smaller master piston
The force pushing down will put the liquid under pressure
The pressure is transmitted through the liquid and against the slave piston
The pressure causes the slave piston to exert a force where it is needed

6. Using the formula P=F/A
What is the pressure exerted on the liquid by the slave piston?
Answer:
Pressure = 10N / 5cm2
= 2 N/cm2
Calculate the area of the slave piston that will lift a 100N load
Area = force / pressure
= 100N / 2 N/cm2
10N
Slave piston
Master
Piston
Is 5 cm2

7. More questions on hydraulics
Master piston = 10cm2
Slave piston = 100cm2
What will the force (F1) need to be to exert a pressure of 20 N/cm2 ?
Calculate the weight (F2) that can be lifted by the slave piston.
Answers: 1. Force = 20 N/cm2 x 10cm2 = 200N
2. Force = 20 N/cm2 x 100cm3 = 2000N

8. Summary of the principles of hydraulics
Pressure is transmitted throughout a liquid
A force may be applied anywhere to the liquid
All hydraulic systems use a small master piston and a large slave piston
A small force is used to create a very big force
The small master piston is used to apply a force
The slave piston is always bigger than the master piston
The larger slave piston will multiply the original force put on the master piston

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