Two movers use a rope system to lift a box to a third-story apartment. They do 1,200 J of work on the rope system, and the rope system does 1,020 J of work on the box. What is the efficiency

Efficiency is defined as the measure of the amount of work or energy is conserved in a certain process. At all times, in every process, work or energy is always lost or wasted due to certain interference. Not all work given is converted to useful work or energy. Thus, efficiency is calculated by dividing the energy or work output to the energy or work input then the value is multiplied by 100 to express efficiency as percentage.

Efficiency = work output / work input

Efficiency = (1020 J / 1200 J) = 85%