What occurs to energy when work is done against resistance?

When work is done against resistance, energy is transformed and typically dissipated as heat. This occurs because resistance, such as friction or air resistance, opposes the motion, requiring energy input to overcome it. As the work is done, the energy expended results in an increase in thermal energy, which is often sensed as heat. This principle is rooted in the laws of thermodynamics, which state that energy cannot be created or destroyed, only transformed from one form to another.

In mechanical systems, when energy is applied to overcome resistance, the majority of that energy ultimately converts into thermal energy due to the interactions at the surfaces or fluids involved. Thus, while there may be other forms of energy involved in these processes (such as kinetic or potential energy), the energy associated with work done against resistive forces primarily manifests as heat losses in practical situations.