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Hydraulics

Hydraulics. How does a hydraulic system work? . Starter: List the main properties of liquids and gases. What are the main similarities/differences between them ? . Glossary words. Pressure – force per unit area acting on surface at right angles to the surface. Unit is pascals (Pa)

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Hydraulics

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  1. Hydraulics 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 5 = F/30 5X30 = F F = 150N P = F/A P = 50/10 = 5Pa

  15. Working out the pressure http://science.howstuffworks.com/transport/engines-equipment/hydraulic1.htm • Force1 F1 is applied is called the effort. • The force exerted F2 is the load. • The load is moved by a smaller effort. P = F1where A1 is the piston area. A1 The pressure acting on the wider piston = PA2 In other words – F2 = F1 X A2 A1

  16. Have a go at the questions

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