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Chapter 5.1 work and energy

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Chapter 5.1 work and energy

  1. 1. Chapter 5Work and Energy
  2. 2. Work• Equal to the magnitude of the force times the magnitude of the displacement (W = Fd)• Done only when the components of a force are parallel to the displacement (Figure 5-2)• Work is not done unless the object is moved
  3. 3. Net Work• Net work = net force x displacement x cosine of angle between them – Cosine 0 degrees = 1 – Cosine 90 degrees = 0• Units are force times length (N x M), or joules• Three push-ups require about 1000 J
  4. 4. Work (cont.)• Scalar• Can be positive or negative (figure 5-3) – Dependent upon force exerted• If net work is positive, the object speeds up• If net work is negative, the object slows down

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