A gasoline engine takes in 1.70×10 4 J of heat and delivers 3900 J of work per c

Question

A gasoline engine takes in 1.70×104 J of heat and delivers 3900 J of work per cycle. The heat is obtained by burning gasoline with a heat of combustion of 4.60×104 J/g .

Part A

What is the thermal efficiency of the engine?

ANSWER: e = _______ %

Part B

How much heat is discarded in each cycle?

ANSWER: Q = ________ J

Part C

What mass of fuel is burned in each cycle?

ANSWER: m = _____ g

Part D

If the engine goes through 62.0 cycles per second, what is its power output in kilowatts?

ANSWER: P = _________kW

Part E

If the engine goes through 62.0 cycles per second, what is its power output in horsepower?

ANSWER: P = _______hp

Explanation / Answer

A) The thermal efficiency of the engine = (3900 J/ 1.7*10^4 J)*100 % = 22.94 %

B)   Heat Discarded = Heat Taken in - Heat Delivered
= 1.7*10^4 J - 3900 J = 13100 J

C)   Mass = (Heat taken in) / (Heat of Combustion)
= (1.7*10^4 J)/ (4.6*10^4 J/g) = 0.3695 g

D)   Power Output = Heat Delivered per unit time = Total Heat Delivered / time
= Heat Delivered per cycle * Cycles per second
= (3900 J) X (62 /sec) = 241800 W = 241.8 kW

E)   Power Output (Horsepower) = (241.8 kW) 1.34 HP/kW) = 324.012 HP

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