1 attempts left Check my work Be sure to answer all parts. A woman expends 93 kJ

Question

1 attempts left Check my work Be sure to answer all parts. A woman expends 93 kJ of energy in walking a kilometer. The energy is supplied by the metabolic breakdown of food intake and has a 35 percent efficiency If the woman drives a car over the same distance, how much energy is used if the car gets 8.0 km per liter of gasoline (approximately 20 mi/gal)? The density of gasoline is 0.71 g/mL, and its enthalpy of combustion is 49 kJ/g. .7 Compare the efficiencies of the two processes. (driving kJ (walking) 8

Explanation / Answer

Basis is 1 Km distance

1 gallon= 3.78 Liter

8 km requires 3.78 liters

or 1 km requires 3.78 liters/8= 0.4725 liters of gasoline, 1000ml =1 L

volume of gasoline required per km= 0.4725*1000= 472.5 ml

Density = 0.71 g/ml, mass of gasoline= 472.5ml*0.71 g/ml= 335.5 gm of gasoline

energy spent per gm= 42 Kj

energy supplied= 335.5 gm* 42 Kj/gm= 14091 Kj

2. When 93 Kj of energy is spent with 35% efficiency, energy actually supplied= 93/0.35= 265.7 Kj

Efficiency of the proces= Energy used during driving/energy used while walking =14091/265.7= 53

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