SG_Chap5 - Chapter 5 Energy 5.1 Work Work = F. Dx 5.1 Work...

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Page 1 5.1 Work Work = F. D x Chapter 5 Energy 5.1 Work • The work, W , done by a constant force on an object is defined as the product of the component of the force along the direction of displacement and the magnitude of the displacement • This gives no information about – the time it took for the displacement to occur – the velocity or acceleration of the object • Work is a scalar quantity
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Page 2 Work – F is the magnitude of the force – Δ x is the magnitude of the object’s displacement q is the angle between x ) cos F ( W D q and D Fx Work done example The total mass of fish and sled = 50 kg. F = 120 N and he pulls it for 5 m. How much work is done if q = 0 How much work is done if q = 30 o
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Page 3 When Work is Zero • Displacement is horizontal • Force is vertical • cos 90 = 0 Work Can Be Positive or Negative • Work is positive when lifting the box • Work would be negative if lowering the box – The force would still be upward, but the displacement would be downward
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Page 4 5.2 Kinetic Energy • Energy associated with the motion of an object • Scalar quantity with the same units as work • Work is related to kinetic energy 2 mv 2 1 KE 5.2 The Work-Energy Theorem and Kinetic Energy • Energy: when work is done, energy changes • Many forms of energy: chemical energy, nuclear energy, electric/magnetic energy, mechanical energy … – Total energy is conserved • Energy can do things
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Page 5 Work and Kinetic Energy • An object’s kinetic energy can also be
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SG_Chap5 - Chapter 5 Energy 5.1 Work Work = F. Dx 5.1 Work...

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