How is the efficiency of a pulley system affected by friction?

The efficiency of a pulley system is greatly impacted by the presence of friction, which can cause energy loss within the system. When friction occurs in the components of a pulley system—such as in the bearings, between the ropes and the pulley surface, or in the axle—it converts some of the mechanical energy into heat instead of using it for lifting or moving loads. This dissipation of energy results in reduced efficiency because not all the input energy is effectively used for work.

In a highly efficient system, ideally, all the energy input would be transmitted directly to the load being lifted. However, in practical scenarios, increased friction leads to a proportion of this energy being wasted. Therefore, as friction increases in a pulley system, the overall efficiency declines due to this energy loss, making option C the accurate depiction of the relationship between friction and efficiency in a pulley system.