7. A stereo is able to convert 20% of its electrical energy into sound. If 1000 J of sound energy is produced, calculate the electrical energy used [Show all work].

8. A vehicle is only 18% efficient. How was the other 82% of the energy lost?

7) Electrical Energy used = 5000 J

8) Check below for answer and explanation

Explanation:

7) Let the Sound Energy Produced = SE

Electrical Energy = EE

Sound energy produced, SE = 1000 J

% of Electrical energy converted to sound = 20%

SE = 20% of EE

SE = (20/100) * EE

1000 = 0.2 EE

EE = 1000/0.2

EE = 5000 J

Electrical Energy used = 5000J

8) The vehicle's efficiency = 18%

Energy loss = 82%

The 82% energy loss in the vehicle can be due to the following reasons:

a) Heat generated by the exhaust of the vehicle

b) Noise generated by the vehicle

c) Frictional force in the engine

d) Combustion

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