1000 joules of energy are put i to a pulley system and 400 joules come out. what does the law of conservation of energy imply about the lost energy

According to the law of conservation of energy, energy cannot be created or destroyed, it can only be transferred or transformed from one form to another. In this case, the lost energy (600 joules) implies that it has been transformed into another form, such as heat or sound. It could also be possible that there could be inefficiencies in the system, resulting in energy losses due to friction or other factors.