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Work and Power. Chapter 14. Work and Power. Work in physics is not the same as the everyday meaning of work… Work - the product of force and distance -the transfer of energy Work is done when a force is exerted on an object and that object moves Work requires motion

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Work and power

Work and Power

Chapter 14


Work and power1
Work and Power

  • Work in physics is not the same as the everyday meaning of work…

    • Work- the product of force and distance

      -the transfer of energy

      • Work is done when a force is exerted on an object and that object moves

        • Work requires motion

        • For a force to do work on an object, some of the force must act in the same direction as the object moves. If there is no movement, no work is done


Work and power2
Work and Power

  • Work

    • Work depends on Direction

      • Any part of a force that does not act in the direction of motion does no work on an object

        • See figure 2-B


Work and power3
Work and Power

  • Calculating Work

    • Work = Force x Distance

      • Force in newtons (N)

      • Distance in meters (m)

      • Work in joules (J)

    • Sample Problem: A weight-lifter applies force to a 1600 N barbell, to lift it over his head (a height of 2.0 m). How much work is done by the weight-lifter?

      • W = F x D


Work and power4
Work and Power

  • Power- is the rate of doing work

    • Doing work at a faster rate requires more power. To increase power, you can increase the amount of work done in a give time, or you can do a given amount of work in less time.


Work and power5
Work and Power

  • Calculating Power

    • Power = Work/Time

      • Work in joules (J)

      • Time in seconds (s)

      • Power in watts (W)

        • One watt is equal to one joule per second

    • Sample Problem: When you lift a box, work is done (1340 J). It takes you 1.8 seconds to lift the box. How much power is done?

      • P = W/t


Work and power6
Work and Power

  • Sample Problem:

    • You exert a vertical force of 88 N to lift a box to a height of 1.5 m in a time of 2.3 seconds. How much power is used to lift the box?

      • W = FxD & P = W/t


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