Question

A car engine produces an average of 25 kW of power in a period of 10-min during which 1.25 kg of gasoline is consumed. If the heating value of gasoline is 43,000 kJ/kg, the efficiency of this engine during this operation is:

A. 24%B. 28%C. 32%D. 36%

Answer 1

Answer:B

Step-by-step explanation:

Given

Power Produced
`P=25\ kW`

time
`t=10\ min`

Gasoline consumed
`m=1.25\ kg`

Heat capacity of Gasoline
`C=43,000\ kJ/kg`

Heat Provided by Gasoline
`Q_s=m* C`

`Q_s=1.25* 43000=53,750\ kJ`

Energy used in Producing Power is
`W=25* 10* 60=15,000\ kJ`

Efficiency of an engine is

`\eta =(Work)/(Energy\ Supplied)`

`\eta =(15000)/(53750)=0.2790`

`\eta =27.90\approx 28\ \%`