Question

what limits the amount of work that a system can do?

Explanation:

In physics, the available energy and inefficiencies like friction and heat loss limit work. Energy constraints mean there's only so much energy to convert into work. Inefficiencies cause energy to be dissipated as non - useful forms, reducing the amount of work output.

Answer:

The available energy and inefficiencies (such as friction and heat loss) in the system limit the amount of work it can do.