Work has nothing to do with energy expenditure

Abstract

We show that, contrary to common sense, the author of mechanical work does not necessarily provide the required energy. By the most simple example one can ever conceive -a standing person starting to move, this point is made clear: the floor does not spend energy and it does work on the person (in relation to its own reference frame). We analyse two additional examples in order to ilustrate the subtle aspect of Newtonian theory: despite something is said about where the work is going to, namely the Work -Kinetic Energy Theorem, absolutely nothing is said about where the work comes from (we explain in our conclusions, making reference to Aristotelian philosophy, why it happens in that way). In all these examples, explicit calculations of work are done in both inertial and non-inertial frames.