A car converts 1000 J of energy from a sample of fuel. 750 J of heat (thermal energy) is produced by the engine, 150 J of heat is produced in the transmission, drive train, etc., and 100 J of work is done to move the car. How efficient was the process of burning fuel for the car?
To calculate the efficiency of the car's fuel burning process, we need to compare the useful work output to the total energy input.
Efficiency is commonly defined as the ratio of useful energy output to the total energy input. In this case, the useful energy output is the work done to move the car, which is given as 100 J. The total energy input is the sum of the heat produced by the engine (750 J) and the heat produced in the transmission, drive train, etc. (150 J), giving a total of 900 J.
The formula to calculate efficiency is:
Efficiency = (Useful energy output / Total energy input) * 100
Using the values given, we can substitute them into the formula:
Efficiency = (100 J / 900 J) * 100
Calculating this expression, we find:
Efficiency ≈ 11.1%
Therefore, the efficiency of the car's fuel burning process is approximately 11.1%.