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# 2008 Simple Machines

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• ### 2008 Simple Machines

1. 1. <ul><li>Notes: Machines </li></ul><ul><li>CW: Man & Machines </li></ul><ul><li>H: Simple Machines </li></ul>
2. 2. Machines April 15, 2009
3. 3. Objectives <ul><li>Explain how a machine makes work easier </li></ul><ul><li>Calculate mechanical advantage </li></ul><ul><li>Describe an ideal machine </li></ul><ul><li>Explain why machines are not 100% efficient </li></ul>
4. 4. History of Work
5. 5. Simple Machines
6. 6. <ul><li>Machines make work easier. </li></ul><ul><li>W = F x D </li></ul><ul><li>The two most common resistive forces are friction and gravity </li></ul>Machines
7. 7. Simple Machines <ul><ul><li>a device that does work with only one movement </li></ul></ul>
8. 8. Types of Simple Machines <ul><li>inclined plane </li></ul><ul><li>wedge </li></ul><ul><li>lever </li></ul><ul><li>wheel & axle </li></ul><ul><li>screw </li></ul><ul><li>pulley </li></ul>These make work easier !
9. 9. Machines make work easier by changing <ul><li>the amount of force you exert </li></ul><ul><li>the distance over which you exert your force </li></ul><ul><li>the direction over which you exert your force </li></ul>
10. 11. <ul><li>when using a machine to do work </li></ul><ul><ul><li>Effort (Input) Force (F E ) –the force you apply to the machine </li></ul></ul><ul><ul><li>Resistance (Output) Force (F R ) –the force that the machine applies </li></ul></ul>2 forces involved
11. 12. <ul><li>Work In (W in ) – The work done on the machine (energy put into the machine) </li></ul><ul><li>Work Out (W out ) – The work done by the machine (energy put out by the machine) </li></ul>2 types of work involved
12. 13. Mechanical Advantage <ul><li>The number of times a machine increases a force exerted on it </li></ul><ul><li>MA = output force / input force </li></ul>
13. 14. Machines make work easier by changing <ul><li>1. the amount of force you exert </li></ul><ul><li>the MA is greater than 1 </li></ul><ul><li>2. the distance over which you exert your force </li></ul><ul><li>the MA is less than 1 </li></ul><ul><li>3. the direction over which you exert your force </li></ul><ul><li>the MA is equal to 1 </li></ul>
14. 15. Efficiency <ul><li>Compares the output work to the input work. </li></ul><ul><li>Efficiency = W out x 100% </li></ul><ul><li> W in </li></ul><ul><li>The higher the percent, the more efficient the machine. </li></ul>
15. 16. <ul><li>one in which there is no friction, no energy is lost so W in =W out </li></ul><ul><li>In reality, work out will always be less than work in because energy is lost through friction </li></ul>Ideal machine