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Chapter 5.2 Physical Science WZPP ps Ok web post

Using Machines. Chapter 5.2 Physical Science WZPP ps Ok web post. What is a Machine?. Something that makes work (force x distance) easier Does not need to be powered Can be powered by the force of a person. Making work easier. Increasing the force applied to an object

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Chapter 5.2 Physical Science WZPP ps Ok web post

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  1. Using Machines Chapter 5.2 Physical Science WZPP ps Ok web post

  2. What is a Machine? • Something that makes work (force x distance)easier • Does not need to be powered • Can be powered by the force of a person

  3. Making work easier • Increasing the force applied to an object • You can do the same amount of work by applying a small force over a greater distance • or • a large force over a short distance • See the jack example: • figure 6, page 132

  4. Making work easier • Increasing the distance • Work stays the same • When you increase the distance, less force will be needed

  5. Making work easier • Changing Directions • This can be to the sides or opposite direction

  6. Work Done by Machines • Two kinds of forces need to be considered when using machines • Work I do on the machine (Win) • Work done by the machine (Wout)

  7. Conserving Energy • Amount of energy put in the machine needs to be greater than the energy out of the machine • This is real life • Machines can not create energy • Some energy is lost as friction

  8. Ideal Machine • Is a perfect machine • No friction, no mass, no weight • So • Win = Wout(remember, F x D = W) • So • (Effort Force x Effort Distance = Resistance force x resistance distance) Fe x De = Fr x Dr 5.2B ws

  9. Mechanical Advantage (MA) • Is the number of times a machine multiples an effort force • Mechanical advantage = resistance force divided by the Effort force • M A = Fr / Fe

  10. Efficiency • Is the measure of how much work put into a machine is changed into useful work by the machine • High efficiency machines produce less heat from friction • Efficiency is Wout / Win x 100%

  11. Efficiency • Efficiency of real machines is always less than 100% • Machine can be made more efficient by reducing friction • Add lubricant– oil, grease end notes 5.2 ps 5.2C ws

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