The efficiency of a machine can be increased by decreasing distance. decreasing force. reducing friction. reducing work.

Reducing friction

Explanation:

Friction refers to the resistance that a surface encounters while moving on the surface of another. Machines often posses moving parts such as rollers. Those parts move on other surfaces generating friction. Friction in machine parts leads to useless work and reduces the amount of input work used by the machine to do useful work. The efficiency of a machine has to do with its ability to convert input work into output work. This efficiency is greatly reduced by friction in the moving parts of the machine. Hence friction decreases the efficiency (work done by a machine)

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.