Mechanical Systems

1. Mechanical Systems

2. 6 Types of Simple Machine • Simple Machine: Machine with no moving parts. Device used to do work. • Levers • Inclined Plane/Wedge • Wheel and Axle • Pulley • Gear • Screw http://eschooltoday.com/science/simple-machines/introduction-to-simple-machines.html

3. Topic 1 Key Terms • Lever • Fulcrum • Effort Force • Load • Effort Arm • Load Arm • 1st Class Lever • 2nd Class Lever • 3rd Class Lever • Work • Inclined Plane • Input work • Output work

4. Topic 1: Levers and Inclined Planes • Lever: a simple machine that changes the amount of force you must exert in order to move an object. • http://www.edumedia-sciences.com/en/media/675-principle-of-the-lever • A lever consists of: • A bar that is free to rotate around a fixed point • Fulcrum: the fixed point that supports the lever

5. Effort Force: the force that you exert on a lever to make it move. • Load: the mass of an object that is moved or lifted by a machine.

6. Effort Arm: the distance between the fulcrum and the effort force • Load Arm: the distance between the fulcrum and the load

7. 1st Class Lever • http://www.edumedia-sciences.com/en/media/751-types-of-levers • The fulcrum is between the effort and the load. This class of lever can be used for either power or precision.

8. 2nd Class Lever • Always exerts a greater force on the load than the effort force you exert on the lever. In this type of lever, the load is between the effort and the fulcrum.

9. 3rd Class Levers • The effort is exerted between the fulcrum and the load. When using this class lever, you must exert a great force on the lever than the lever exerts on the load. However, the load can be moved very quickly. • htt/simpMach/sm1.swf

10. In his LFE the ELF FEL once

11. Which type of lever?

12. The Inclined Plane • It is a ramp or slope that reduces the force you need to exert to lift something. • They are also considered a simple machine. • http://www.edumedia-sciences.com/en/media/833-the-inclined-plane

13. What is Work? • Work is when you exert a force on an object and move that object some distance in the direction of the force. • It is an energy in action and measured in joules (J) • Work (J)= Force (N) X Distance (m)

14. Using W = F x D • Calculate the distance a box can be moved if you exert a force of 45 N and only want to use 600 J. • Calculate the amount of force needed to lift a box 0.5 m, using only 50 J. • Calculate the amount of work needed to move a box 500m, with a force of 35 N.

15. Practice • Leonard lifted a 60N chair from the floor and placed it on top of a table .8m high. How much work did he do? • Hanna did 10 000J of work while pushing with a force of 500N to pull a wagon 20m across the floor. How far did she move the wagon? • 30J of work was required to lift a box 2.0m to a shelf. What was the weight of the box? • How much work does an elephant do while moving a circus wagon 20 meters with a pulling force of 200N? •  Tommy does 15 Joules of work to push the pencil over 1 meter. How much force did he use? • Angela uses a force of 25 Newtons to lift her grocery bag while doing 50 Joules of work. How far did she lift the grocery bags?

16. Work Input and Work Output • The work you do on a machine is called input work. • The work the machine does on the load is the output work. • A machine never does more work on the load than you do on the machine. • Machines make work easier because they change the size or direction of the force exerted on the machine.

17. Mechanical Advantage • the ratio of the force produced by a machine to the force applied to it, used in assessing the performance of a machine. • The greater the mechanical advantage is, the easier it is • The lower the mechanical advantage is, the harder it is

18. Topic 2 Key Terms • Winch • Gear • Gear Train • Driving Gear • Driven Gear • Pulley • Axle • Speed Ratio

19. Calculating work review • Calculate the force needed to drag a log 11m, doing 1000J of work. • In which situation would you be able to carry the bag farther? Situation A: Doing 800J of work, using 12N or Situation B: Doing 1100J of work using 4N.

20. The Wheel and Axle • Wheel-and-axle combinations come in a variety of shapes and sizes. • “Wheels” do not have to be round. • As long as two turning objects are attached to each other at their centres, and one causes the other to turn, you can call the device a wheel and axle. • A wheel-and-axle device can generate speed. These machines require a large effort force and produce a smaller force on the load. • http://www.cosi.org/files/Flash/simpMach/sm1.swf

21. Wheel and Axle • Winch: consists of a small cylinder and a crank or handle. • The axle of the winch is held in place and acts like a fulcrum. • The handle is like the effort arm of a lever. • Exerting a force on the handle turns the wheel. • The radius of the wheel- the distance from the center of the wheel to the circumference- is like the load arm on a lever.

22. The force that the cable exerts on the wheel is like the load on a lever. • Since the handle is much longer than the radius of the wheel, the effort force is smaller than the load. • Using a winch is like using a short lever over and over again.

23. Gearing Up • Gear: a rotating wheel-like object with teeth around its rim. • Gear Train: a group of two or more gears. The teeth of one gear fit into the teeth of another. When the first gear turns, its teeth push on the teeth of the second gear, causing the second gear to turn. • http://www.edumedia-sciences.com/en/media/391-gears

24. Driving Gear (driver; or first gear): may turn because someone is turning a handle or because it is attached to a motor. • Driven Gear (second gear; or follower): the gear turned by the driving gear.

25. Going the Distance • http://www.edumedia-sciences.com/en/media/550-bicycle-gear-ratios • Think about the gears on a bicycle. One set of gears is attached to the pedals and the other to the rear wheel. • A chain connecting the gears allows the front gear to turn the gear on the rear wheel, some distance away. • Sprocket: a gear with teeth that fit into the links of a chain. • Speed Ratio: the relationship between the speed of rotations of a smaller gear and a larger gear. • Speed Ratio= #of driver gear teeth / # of follower gear teeth

26. Speed Ratio Practice • Calculate the speed ratio if the driver gear has 45 teeth and the follower gear has 18 teeth • Calculate the speed ratio if the driver gear has 45 teeth and the follower gear has 16 teeth.

27. Think about it! • If you are trying to win a race and your driver gear has 55 teeth, should you use the follower gear with 5 teeth or 9 teeth? Which one would use? • If you want your speed ratio to be higher than 2, which of the following follower gears would you use: 11, 12 or 17? The driver gear has 60 teeth.

28. Pulleys • Pulley: a grooved wheel with a rope or chain running along the groove. • A pulley is like a class 1 lever. Instead of a bar, a pulley has a rope. The axle of the pulley acts like a fulcrum. The two sides of the pulley are the effort arm and the load arm. • http://www.edumedia-sciences.com/en/media/408-pulleys

29. Screws • A screw is simply an inclined plane around a cylinder.  • To describe this better you can view it as a cylinder with a head (solid top) at one end and a pointed tip (like a nail) at the other end. More importantly, it has ridges winding around it. • The correct term for the ridges (or grooves) around the cylinder is the thread. • The distance between threads is called the pitch. **The closer the distance is, the greater the mechanical advantage**

30. Topic 3 Key Terms • Kinetic Energy • Potential Energy • Efficiency • Lubrication

31. Work and Energy • Kinetic energy is the energy of motion. An object which has motion - whether it be vertical or horizontal motion - has kinetic energy. • There are many forms of kinetic energy – • vibrational (the energy due to vibrational motion), • rotational (the energy due to rotational motion), • translational (the energy due to motion from one location to another).

32. Stored Energy • Potential energy is the stored energy of position possessed by an object. An object can store energy as the result of its position. • For example, the heavy heavy ball of a demolition machine is storing energy when it is held at an elevated position. This stored energy of position is referred to as potential energy. This stored energy of position is referred to as potential energy..

33. Energy Transmitters • Energy or power can be transmitted. It is transmitted from one place to another, and no energy is changed or converted. • This was found in the Law of Conservation of Energy – Energy cannot be created or destroyed but can change forms • YouTube - How Manual Transmissions Work

34. No Machine is 100% Efficient • An ideal machine would transfer all of the energy it received to a load or to another machine. • REAL MACHINES ARE NOT THIS EFFECTIVE---some of the energy is always lost! • Efficiency tells you how much of the energy you gave to the machine was transferred to the load of the machine. • efficiency = work output / work input

35. Improving Efficiency • The key to improving efficiency is to reduce friction. This is done by lubricating the gears, pulleys etc. • Machines burn less fuel, are more effective and last longer when there is less friction.