Final answer:
The efficiency of a simple machine is always less than 100 percent because some of the input work is converted into heat because of friction; this is true for all simple machines.
Step-by-step explanation:
The question posed deals with the efficiency of simple machines and whether it is true or false that the efficiency is always less than 100 percent. The answer to this question is true. The efficiency of a simple machine is indeed always less than 100 percent owing to the unavoidable conversion of some input work into heat energy because of friction. For example, when you use a lever to lift a heavy object, some of the energy you apply is dissipated as heat due to the friction at the pivot point. This is also true for other types of simple machines, such as pulleys, inclined planes, screws, and wheel and axles.