Answer:
The amount of mechanical energy produced by the old lorry when 600 Joules of chemical energy have been used by the engine, M.E. is 120 Joules
Explanation:
The question is a word problem on the relationship between energy efficiency and energy consumption
The given parameters of the old lorry are;
The chemical energy to mechanical energy conversion efficiency of the old lorry = 20%
The amount of chemical energy used by the engine = 600 joules
Let 'M.E.' represent the amount of mechanical energy produced by the old lorry, we have;

Therefore, the for the old lorry, we have;

∴ M.E. Produced = 20/100 × 600 J = 120 J
The amount of mechanical energy produced by the old lorry when 600 Joules of chemical energy have been used by the engine, M.E. = 120 Joules