By calculating thermal efficiency, the input energy is 10,000 joule.
We need to know about the thermal efficiency to solve this problem. Thermal efficiency is the ratio of work done by the machine to input energy. It can be determined as
η = W / Qinp
where η is thermal efficiency, W is work and Qinp is input energy.
From the question above, we know that:
η = 40%
W = 400 J
By substituting the following parameter, we get
η = W / Qinp
40% = 400 / Qinp
Qinp = 400 x 100/40
Qinp = 10,000 joule
Hence, the input energy of a car engine is 10,000 joule.
For more on thermal efficiency at: brainly.com/question/24159924
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