Calculate the efficiency of a runner who produces of 500J of kinetic energy from 2500J of chemical energy.
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Answer:
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Explanation:
Energy Efficiency Practice Problems
1. Calculate the energy efficiency of a light bulb that gives of 40J of light from 200J
of electrical energy.
(40J/ 200J) X 100 = 20%
2. Calculate the energy efficiency of a motor that does of 60J of work from 240J of
electrical energy.
(60J/240J) X 100 = 25%
3. Calculate the energy efficiency of a radio that gives of 30J of sound from 360J of
electrical energy.
(30J/360J) X 100 = 8.33%
4. Calculate the efficiency of a runner who produces of 500 J of kinetic energy
from 2500J of chemical energy.
(500J/2500J) X 100 = 20%
5. What is the amount of useful energy from a bulb whose energy efficiency is 25%
when supplied with 600J of energy?
25%/100 = X/600J
Useful energy = 150 J
6. The burning gasoline in an engine contains 2000 J of chemical energy. 1200 J of
this energy becomes kinetic energy, and 800 J are lost to friction. What is the
energy efficiency of the engine?
(1200J/ 2000J) X 100 = 60%
7. A child uses a sling-shot to propel a rock into the air. When the child pulls
on the elastic part of the sling shot, it stores 500 J of energy. When the
child lets go, the rock moves with 400 J of kinetic energy and 100 J are lost
to friction. What is the energy efficiency of this sling shot?
(400J/500J) X 100 = 80%