A car is driven along a level road. The total energy is put from the petrol is 60 KJ and the car wastes 45KJ of energy. What is the efficiency of the car?
Question
A car is driven along a level road. The total energy is put from the petrol is 60 KJ and the car wastes 45KJ of energy. What is the efficiency of the car?
Solution
The efficiency of any machine or system is calculated by the ratio of useful output energy (or power) to the total input energy (or power). It is usually expressed in percentage.
In this case, the total energy input is 60 KJ and the wasted energy is 45 KJ. Therefore, the useful output energy is the total energy input minus the wasted energy, which is 60 KJ - 45 KJ = 15 KJ.
Now, we can calculate the efficiency as follows:
Efficiency = (Useful output energy / Total input energy) * 100%
Substituting the given values:
Efficiency = (15 KJ / 60 KJ) * 100% = 25%
So, the efficiency of the car is 25%.
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