Levers

1. Cars Levers

2. Machines Can a 50kg driver stop a 1000kg car? Starter – List at least 10 machines in your home that use forces (think about moments and pressure)

3. Machines Machines use forces in all sorts of ways .... 3m 1m 1m 500N 100N

4. Machines A machine is anything that helps you do things more easily. The most common simple machines are; levers, pulleys, inclined planes (ramps), screws and gears. Complex machines such as cranes, winches, clocks and bicycles contain many simple machines.

5. Machines- magnify the forces you use Think of a can opener where you usually turn a big knob, handle or wheel. The effort you put into turning the handle or wheel moves a smaller wheel which in turn moves a circular blade that pierces and slices open the can as it moves. You are turning a large wheel or knob and this requires much less effort than turning the little wheel by itself. In this way the can opener has magnified the force you use. In other words, you have a greater force for less effort.

6. Machines – Can speed things up When you ride a bicycle and push down on the pedals, the pedals don’t turn as fast as the back wheel does. A few turns of the pedals can make you go very fast. A machine like the bicycle that does this is said to have a speed advantage or a distance advantage. The higher the gear you use, the faster you go and the more distance you cover.

7. Machines – Can speed things up To go up a hill you put a bicycle into low gear, so that less effort is needed to move the load (you and the bike) up the hill. The bicycle in this case gives you a force advantage.

8. Machines- Can transform energy You do work when you use a force to move something. Energy is the ability to do work. In most simple machines, like a can opener, you are applying a force to move the machine. So you are doing work or providing the energy to get the machine working.

9. Machines- Can transform energy Machines reduce the amount of work or effort required to get a job done. Machines are energy transformers. They take the initial or starting energy and transform or change it into a different form.

10. Using Liquid Pressure • Gas (e.g. air) can be compressed (squashed) but liquid can’t. Explain this in terms of particles! • Pressure applied to a liquid can’t compress (squash) it so it can transfer the pressure • This can be used in machines, e.gcar brakes •  The brake pedal pushes a piston that acts on a liquid that transfers pressure to 4 brake pistons

11. Hydraulics Hydraulic systems use the principle that pressure is transmitted throughout a liquid. They are used to transfer movement from one part of a machine to another without linking them mechanically. All hydraulic systems use two pistons linked via a pipe carrying a special oil called hydraulic fluid. Force applied here Force transferred here Pressure inside all parts of the hydraulic system is the same

12. Pressure is constant throughout this liquid Hydraulic Systems • Draw a simple version of this diagram in your booklet. • Explain why the car can be lifted? Liquid is not compressed so pressure on the master = pressure on the slave but pressure is acting over a larger area on the slave, which gives a bigger FORCE.

13. Hydraulic Systems Complete the questions on the worksheet in your booklet

14. Gas Pressure

15. Can a 50kg driver stop a 1000kg car? Machines Review Starter – List at least 10 machines in your home that use forces (think about moments and pressure)

16. Using Science Wheelchairs are examples of science in action. Use the sheet to learn more about this science... ... And design your own wheelchair.

17. Plenary Share your ideas Complete your poster for homework

18. Stored Energy: A hidden hazard! An oil storage vessel at car tyre pressure would release energy equivalent to 1 kg of TNT explosive !!

19. The Boiler House The Boiler !! A factory boiler exploded …

20. OOPS again……. During removal of its twin, the cylinder managed to escape and make a clean get away, clear through the ceiling and onto the roof!

21. Don’t forget Vacuum ! The maximum vacuum that can normally be generated is (only) 1 bar. Vessels designed for large internal pressures can easily collapse if subjected to a vacuum. This tanker was steam cleaned and then its lid was closed. It cooled down, and pressure inside went down…… A baked bean can is far stronger than a large atmospheric storage tank, size for size!

22. Levers Why is it easier to hammer in a nail than take it out? Starter: (1) is it easier to steer a bike holding the middle of the handlebars or the handles? (2) Explain the answer to your partner

23. Explain this … Example 1 1. Knocking a nail in and pulling it out 2. Opening a door – where would you push? 3. Cutting thick card – do you cut at the tip or near the pivot? These are all examples of levers Example 2 Example 3 What is the common idea?

24. In ancient Greece, Archimedes said “Give me a lever, a place to stand, and I will move the Earth.”  Try it yourself…. Hold a pen or pencil between thumb and finger Gently push it with a finger on your other hand • Near where you’re holding it • Then further away • What do you find?

25. Levers Demonstration Levers demonstration Force multiplier

26. What are Levers? A simple machine that makes work easier for use; it involves moving a load around a pivot using a force. Many of our basic tools use levers, including scissors (2 class 1 levers), pliers (2 class 1 levers), hammer claws (a single class 2 lever), nut crackers (2 class 2 levers), and tongs (2 class 3 levers).

27. First Class Lever The pivot (fulcrum) is between the effort and the load. In an off-centre type one lever (like a pliers), the load is larger than the effort, but is moved through a smaller distance.

28. Examples…. Examples of common tools (and other items) that use a type 1 lever include:

29. Second Class Lever The load is between the pivot (fulcrum) and the effort.

30. Examples…

31. Third Class Lever The effort is between the pivot (fulcrum) and the load.

32. Examples…

33. Pivot Effort Load Levers Discuss with other people how and why nut crackers work

34. Levers Why is it easier to hammer in a nail than take it out? Review Starter: (1) is it easier to steer a bike holding the middle of the handlebars or the handles? (2) Explain the answer to your partner

35. Answer the questions using ideas from Tim and Moby: • What does a lever do? • What are the 4 components of levers? • Give an example of a class 1 lever • What happens to the force needed when you increase the distance from the pivot? • Where is the load in a class 2 lever?

36. Match sentence halves: • A lever is… …the force you put in • The pivot/fulcrum… …a simple machine • The effort is… …the force that you move • The load is… …the point a lever turns around • 2. If you push a door closed, it is much easier if you push it near the handle instead of pushing it near the hinges. Explain why. • 3. Janet is trying to lift a log. Describe two things that Janet could do to make lifting the log easier.

37. Analyse Levers Complete the worksheet. Check with your partner Has everyone on the team got the same answer?