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Mechanical Energy & Work

Mechanical Energy & Work. Energy allows us to do useful jobs. There are many different kinds of energy; mechanical energy is potential and kinetic. Work If an object moves due to the application of a force then work is being done on it.

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Mechanical Energy & Work

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  1. Mechanical Energy & Work Energy allows us to do useful jobs. There are many different kinds of energy; mechanical energy is potential and kinetic. Work If an object moves due to the application of a force then work is being done on it. Work done = force x distance in direction of the force The unit of energy is the joule. 1 J = 1 N x 1 m = 1 kg m2 s-2

  2. Note: • 1. Object must move for work to be done ie no work done pushing against a wall. • 2. If force acts at angle to distance moved need trigonometry. Work done = 20 x 10 cos 30 = 173 J

  3. To lift the book onto the table I need to exert a force equal to its weight for a distance equal to the height of the table. Work done = weight x height W = mgh This is stored as gpe in the book. Note: we arbitrarily take the floor as a zero for gpe. Strictly,Dgpe = mgDh This formula applies only for small changes in height i.e g is assumed constant.

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