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# Work

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### Work

1. 1. Work and Simple Machines
2. 2. Simple Machines <ul><li>The six simple machines are: </li></ul><ul><ul><li>Lever </li></ul></ul><ul><ul><li>Wheel and Axle </li></ul></ul><ul><ul><li>Pulley </li></ul></ul><ul><ul><li>Inclined Plane </li></ul></ul><ul><ul><li>Wedge </li></ul></ul><ul><ul><li>Screw </li></ul></ul>
3. 3. Simple Machines <ul><li>A machine is a device that helps make work easier by </li></ul><ul><ul><li>transferring a force from one place to another </li></ul></ul><ul><ul><li>changing the direction of a force increasing the size of a force </li></ul></ul><ul><ul><li>increasing the distance or speed of a force. </li></ul></ul>
4. 4. Mechanical Advantage <ul><li>input force (the force you apply) and the output force (force which is applied to the task). </li></ul><ul><li>When a machine takes a small input force and increases the magnitude of the output force, a mechanical advantage has been produced. </li></ul>
5. 5. The Lever <ul><li>A lever is a rigid bar that rotates around a fixed point called the fulcrum. </li></ul>
6. 6. The 3 Classes of Levers <ul><li>determined by: </li></ul><ul><li>location of the effort </li></ul><ul><li>force and the load </li></ul><ul><li>compared to the </li></ul><ul><li>fulcrum. </li></ul>
7. 7. The workman uses a trolley to move the large packing case. The fulcrum is the wheel. First Class Lever <ul><li>In a first-class lever the fulcrum is located at some point between the effort and resistance forces. </li></ul><ul><ul><li>Common examples of first-class levers include crowbars, scissors, pliers, tin snips and seesaws. </li></ul></ul>
8. 8. Second Class Lever The gardener uses a wheel barrow to lift tools and garden waste. The load is in the centre of the barrow With a second-class lever, the load is located between the fulcrum and the effort force. Common examples of second-class levers include nut crackers, wheel barrows, doors, and bottle openers.
9. 9. Third Class Lever The fisherman catches the fish which becomes the load at the end of the lever. <ul><li>With a third-class lever, the effort force is applied between the fulcrum and the resistance force. </li></ul><ul><ul><li>Examples of third-class levers include tweezers, hammers, and shovels. </li></ul></ul>
10. 10. Wheel and Axle <ul><li>consist of a large wheel connected to a shaft called an axle. </li></ul><ul><li>When either the wheel or axle turns, the other part also turns. </li></ul>
11. 11. Pulley <ul><li>A pulley consists of a grooved wheel that turns freely in a frame called a block. </li></ul><ul><li>A fixed pulley does not rise or fall with the load being moved. </li></ul><ul><li>A moveable pulley rises and falls with the load that is being moved. </li></ul>
12. 12. Inclined Plane <ul><li>An inclined plane is ramp The inclined plane makes it easier to move a weight from a lower to higher elevation. </li></ul>
13. 13. Wedge <ul><li>The wedge is a modification of the inclined plane. Wedges are used as either separating or holding devices. </li></ul>
14. 14. Screw <ul><li>Think of the threads of the screw as a type of circular ramp (or inclined plane). </li></ul>
15. 15. What’s work? <ul><li>A scientist delivers a speech to an audience of his peers. </li></ul><ul><li>A body builder lifts 350 pounds above his head. </li></ul><ul><li>A mother carries her baby from room to room. </li></ul><ul><li>A father pushes a baby in a carriage. </li></ul><ul><li>A woman carries a 20 kg grocery bag to her car? </li></ul>
16. 16. What is work? <ul><li>In science, the word work has a different meaning than you may be familiar with. </li></ul><ul><li>The scientific definition of work is: using a force to move an object a distance </li></ul>
17. 17. Work or Not? <ul><li>According to the scientific definition, what is work and what is not? </li></ul><ul><ul><li>a teacher lecturing to a class </li></ul></ul><ul><ul><li>a mouse pushing a piece of cheese with its nose across the floor </li></ul></ul>
18. 18. What’s work? <ul><li>A scientist delivers a speech to an audience of his peers. </li></ul><ul><li>A body builder lifts 350 pounds above his head. </li></ul><ul><li>A mother carries her baby from room to room. </li></ul><ul><li>A father pushes a baby in a carriage. </li></ul><ul><li>A woman carries a 20 kg grocery bag to her car? </li></ul>
19. 19. What’s work? <ul><li>A scientist delivers a speech to an audience of his peers. No </li></ul><ul><li>A body builder lifts 350 pounds above his head. Yes </li></ul><ul><li>A mother carries her baby from room to room. No </li></ul><ul><li>A father pushes a baby in a carriage. Yes </li></ul><ul><li>A woman carries a 20 km grocery bag to her car? No </li></ul>
20. 20. Formula for work <ul><li>Work = Force x Distance </li></ul><ul><li>The unit of work is a joule </li></ul>
21. 21. W=FD <ul><li>Work = Force x Distance </li></ul><ul><li>Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done? </li></ul>
22. 22. W=FD <ul><li>Work = Force x Distance </li></ul><ul><li>Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done? 200 joules </li></ul><ul><li>(W = 20N x 10m) </li></ul>
23. 23. Power <ul><li>Power is the rate at which work is done. </li></ul><ul><li>Power = Work * /Time </li></ul><ul><li>* (force x distance) </li></ul><ul><li>The unit of power is the watt. </li></ul>