For a car weighing 960 kg, 7.1×10 7 J of work must be done to move the car 20. m

Question

For a car weighing 960 kg, 7.1×107 J of work must be done to move the car 20. miles, ignoring factors such as frictional loss, and assuming an average acceleration of 2.3 m/s2. If the car has a fuel efficiency of 21 mpg, what percentage of the energy released in the combustion is wasted (does not directly contribute to the work of moving the car)?

1.25 × 105 kJ of energy is released in burning a gallon of gasoline.

For a car weighing 960 kg, 7.1×107 J of work must be done to move the car 20. miles, ignoring factors such as frictional loss, and assuming an average acceleration of 2.3 m/s2. If the car has a fuel efficiency of 21 mpg, what percentage of the energy released in the combustion is wasted (does not directly contribute to the work of moving the car)?

1.25 × 105 kJ of energy is released in burning a gallon of gasoline.

Explanation / Answer

Energy released by gallon of fuel,

E0 = 1.25 x 10^5 kJ = 1.25 x 10^8 J

distance covered in 1 gallon of fuel = 21 miles

Work done , W = (7.1 x 10^7)(21/20)

= 7.46 x 10^7 J

wasted energy = E0 - W = 5.04 x 10^7 J

% energy wasted = ((E0 - W) / E0 ) x 100

= 40.3 %

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