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Understanding Machines in Physical Science: Work, Energy, and Efficiency

Discover the principles behind machines in Chapter 5.2 of Physical Science. Learn how machines make work easier by increasing force, distance, and changing directions. Explore concepts such as mechanical advantage and efficiency to understand how machines operate in the real world.

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Understanding Machines in Physical Science: Work, Energy, and Efficiency

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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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