Final answer:
The total mechanical energy (kinetic plus potential energy) of an object remains constant when the only net work done on the object is by conservative forces. The conservation of mechanical energy is represented by the equation KEi + PEi = KEf + PEf, where 'i' represents initial values and 'f' represents final values.
Step-by-step explanation:
When the only type of force doing net work upon an object is a conservative force, the total mechanical energy (KE + PE) of that object remains constant. The principle behind this is known as the conservation of mechanical energy, which can be represented in equation form as KEi + PEi = KEf + PEf, where i and f denote initial and final values, respectively. It's important to note that this principle applies as long as all the forces involved are conservative, meaning that friction and other nonconservative forces are negligible.
In a system where only conservative forces are doing work, such as gravitational or spring forces, the energy can change form between kinetic energy (KE) and potential energy (PE), while the total mechanical energy will remain constant. This is because a conservative force has an associated potential energy and does work without dissipating energy out of the system. In contrast, when nonconservative forces like friction are involved, they do work that alters the mechanical energy by an amount equal to the work they do.