Is mechanical energy always conserved? Why or why not?
Mechanical energy is not always conserved. Explanation: Mechanical energy is the sum of kinetic and potential energy in a system. E m e c h = K + U Mechanical energy is conserved so long as we ignore air resistance, friction, etc. When we don't ignore outside forces, such as those just mentioned, mechanical energy is not conserved. Energy is "lost" to friction in the sense that it is not converted between potential and kinetic energy but rather into heat energy, which we cannot put back into the object. If we expand our system to include the entire universe, total energy is conserved, but mechanical energy is not. When the object comes to rest and all of its energy has been lost to friction, E m e c h = 0
