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Work

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  • 1. Work and Simple Machines
  • 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. 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. 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. The Lever <ul><li>A lever is a rigid bar that rotates around a fixed point called the fulcrum. </li></ul>
  • 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. 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. 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. 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. 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. 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. 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. Wedge <ul><li>The wedge is a modification of the inclined plane. Wedges are used as either separating or holding devices. </li></ul>
  • 14. Screw <ul><li>Think of the threads of the screw as a type of circular ramp (or inclined plane). </li></ul>
  • 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. 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. 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. 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. 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. Formula for work <ul><li>Work = Force x Distance </li></ul><ul><li>The unit of work is a joule </li></ul>
  • 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. 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. 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>

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