How does one define “work”, in a physics context?

Question

I read somewhere – a while ago – that energy was required for any matter to “do work”. Is there a neat way to define what work means, in this sense?

In: 2

Answer 1

Work has the units of energy, so it’s either power * time or it is force * distance. Does that help? It is either the useful stuff your electrical device or engine did for you, or it’s the useful stuff your piston or muscle (or whatever) did for you. It is literally just the energy that you had a use for.

Because energy cannot be created or destroyed, when you put energy into something you get the same amount out. But almost nothing is 100% efficient, so it is sensible to divide the energy output into *useful* (work) and *not useful* (losses, e.g heat).