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6.7  Power

6.7  Power. 6.7  Power. The idea of power incorporates both the concepts of work and time. 6.7  Power. The idea of power incorporates both the concepts of work and time. Power is work done per unit time. 6.7  Power. The idea of power incorporates both the concepts of work and time.

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6.7  Power

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  1. 6.7 Power

  2. 6.7 Power The idea of power incorporates both the concepts of work and time.

  3. 6.7 Power The idea of power incorporates both the concepts of work and time. Power is work done per unit time.

  4. 6.7 Power The idea of power incorporates both the concepts of work and time. Power is work done per unit time. Average power, P is the average rate at which work W is done, and it is obtained by dividing W by the time t required to perform the work:

  5. 6.7 Power The idea of power incorporates both the concepts of work and time. Power is work done per unit time. Average power, P is the average rate at which work W is done, and it is obtained by dividing W by the time t required to perform the work:

  6. TABLE 6.3      Units of Measurement for Power System Work ÷ Time = Power SI joule (J) second (s) watt (W) CGS erg second (s) erg per second (erg/s) BE foot · pound (ft · lb) second (s) foot ·pound/sec (ft · lb/s) Units

  7. Metabolic Rates for a young 70-kg male

  8. Forms of Energy So far we have considered the following forms of energy: Kinetic energy, Gravitational potential energy, and Mechanical energy. Some of the other forms of energy are: Electrical energy, Chemical energy, Nuclear energy, Thermal energy, and Radiant energy.

  9. Energy Transformations Q: Give an example where gravitational potential energy is converted into kinetic energy?

  10. Energy Transformations Q: Give an example where gravitational potential energy is converted into kinetic energy? A: Falling object.

  11. Energy Transformations

  12. Energy Transformations in the Human body Part of the chemical energy stored in food is transformed into the kinetic energy of physical activities and into the thermal energy needed to keep our bodies at a temperature near 98.6 °F.

  13. Energy Transformations in an Automobile In an automobile chemical energy of gasoline is converted into kinetic energy, as well as electrical energy (to operate the radio, headlights, and air conditioner), and heat (to warm the car during the winter).

  14. The CONSERVATION OF ENERGY Whenever energy is transformed from one form to another, it is found that no energy is gained or lost in the process; the total of all the energies before the process is equal to the total of the energies after the process. This observation leads to the conservation of energy:

  15. The CONSERVATION OF ENERGY Whenever energy is transformed from one form to another, it is found that no energy is gained or lost in the process; the total of all the energies before the process is equal to the total of the energies after the process. This observation leads to the conservation of energy: Energy can neither be created nor destroyed, but can only be converted from one form to another.

  16. The CONSERVATION OF ENERGY Whenever energy is transformed from one form to another, it is found that no energy is gained or lost in the process; the total of all the energies before the process is equal to the total of the energies after the process. This observation leads to the conservation of energy: Energy can neither be created nor destroyed, but can only be converted from one form to another. Learning how to convert energy from one form to another more efficiently is one of the main goals of modern science and technology.

  17. Force versus Distance Graph Work = Area under the Force versus Distance graph

  18. Work Done by a Variable Force The work done by a variable force in moving an object is equal to the area under the graph of F cosq   versus s.

  19. Work and the Compound Bow Find the work that the archer must do in drawing back the string of the compound bow in Figure 6.22 from 0 to 0.500 m.

  20. Problem 65 The drawing shows the force-versus-displacement graph for two different bows. These graphs give the force that an archer must apply to draw the bowstring. (a) For which bow is more work required to draw the bow fully from S = 0 to S = 0.5m? Give your reasoning. (b) Estimate the additional work required for the bow identified in part (a) compared to the other bow.

  21. Conceptual Question 17 The drawing shows an empty fuel tank being released by three different jet planes. At the moment of release, each plane has the same speed and each tank is at the same height above the ground. However, the directions of travel are different. Air resistance is neglected. Q1: Which tank will reach the ground first? Q2: What can you say about the speed of the tanks at ground level?

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