Answer:
20%
Explanation:
Efficiency of an engine is a ratio in percentage of the work done to the energy intake of the engine.
η=(q₁-q₂)/q₁×100%
η is efficiency, q₁ is the energy intake, q₂ is energy wasted.
the information provided is:
energy intake = 400 j
work done = 80 j = (400-320) =q₁-q₂
energy wasted =320 j
η= 80/400×100%
=20%
