Calculate the efficiency of the following devices:
A lawnmower which converts 143 J out of every 450 J of electrical input energy into sound and heat. The rest of the energy is converted to kinetic energy of the blades attached to the motor.
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Expert's answer
2020-07-08T13:14:35-0400
The useful work done by the lawnmower is: 450J−143J=307J. By definition, the efficiency is the ration of the useful work and total input energy. Thus:
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