An automobile engine takes in 4000 j of heat and performs 1100 j of mechanical work in each cycle. (a) calculate the engine's ef

Question

gavmur

1 month ago

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An automobile engine takes in 4000 j of heat and performs 1100 j of mechanical work in each cycle. (a) calculate the engine's ef

ficiency. (b) how much heat is "wasted" in each cycle?

Physics

1 answer:

Sav [3.1K] · Answer 1 · 2026-02-26T00:03:50+03:00

(a) Efficiency in an engine is determined by comparing the work the engine produces to the heat it absorbs:
$\eta= \frac{W}{Q_{in}}$
In this case, the engine performs a work of $W=1100 J$ while taking in $Q_{in}=4000 J$ amount of heat, meaning its efficiency equates to
$\eta= \frac{1100 J}{4000 J}=0.275 = 27.5 \%$

(b) The machine receives 4000 J of heat in each cycle; from this input, only 1100 J is used for productive work, which indicates that the remaining heat is wasted. Therefore, to find wasted heat, one must subtract the work accomplished by the engine from the total heat input:
$Q_{wasted}=Q_{in}-W=4000 J-1100 J=2900 J$