A stage crew member uses a pulley system to lift scenery for the school play. If he does 750 J of work and the pulley system does 600 J of work, what is the efficiency of the pulley system?
The efficiency of a machine is given by the formula:
efficiency = useful work output / total work input
In this case, the useful work output is the work done by the pulley system, which is 600 J. The total work input is the sum of the work done by the crew member and the work done by the pulley system, which is 750 J. Plugging in these values into the formula, we get:
efficiency = 600 J / 750 J = 0.8
Therefore, the efficiency of the pulley system is 0.8 or 80%.