1. How does a hydraulic system work?
Starter:
List the main properties of liquids and gases.
What are the main similarities/differences between them ?

2. Glossary words
Pressure – force per unit area acting on surface at right angles to the surface. Unit is pascals (Pa) Hydraulic pressure- the pressure in the liquid in a hydraulic arm.

3. Which is the best shoe for the job and why?
Walking on snow
Gripping better on mud
Ice skating
Sinking into the mud D b A C

4. Why do you not get spiked to death on this ?

5. Pressure recap Pressure is force per unit area ….
Pressure (Pa) = Force/ area
Have a go at these questions.
Force 50N on a stiletto of 5 m2
Force of 100N on a shoe of 0.3m2
Pressure is 70 Pa, force is 20N what is the area?

6. Demo Why do the leaks in the bottle all travel the same distance?
Observe: pressure increases with depth.

7. Hydraulic Machines Force MULTIPLIERS
How much effort would you have to put into stop a car like this ….

8. Instead we use a force multiplier

9. Demo: syringes

10. Hydraulics
Pressure is the same throughout liquids and is virtually incompressible. (volume wont change with pressure). A force exerted on a liquid is transmitted through the liquid. Even better….. The force can be multiplied by increasing the area where the force acts!

11. Uses of hydraulics

12. Check point
Hydraulic systems are called Force Multipliers.
Why?

13. Lifting a big weight with a small force…

14. Lifting a big weight with a small force…
Force 1 (F1) = effort
Force 2 (F2) = Load
Area 1 (A1) = 10 cm2
Area 2 (A2) = 30 cm2
1) Work out the pressure on the effort.
2) Work out the pressure on the load.
P = F/A
P = 50/10 = 5Pa
P = F/A
5 = F/30
5X30 = F
F = 150N

15. Working out the pressure
Force1 F1 is applied is called the effort.
The force exerted F2 is the load.
The load is moved by a smaller effort.
P = F1 where A1 is the piston area. A1
The pressure acting on the wider piston = PA2
In other words – F2 = F1 X A2

16. Have a go at the questions