To find the efficiency of a pulley system, you need to know the work input and work output. Efficiency is calculated as the ratio of the work output to the work input, multiplied by 100%.
To find the efficiency of a pulley system, you need to know the work input and work output. Efficiency is defined as the ratio of the work output to the work input, multiplied by 100%.
Work input = force input x distance input
Work output = force output x distance output
Efficiency = (Work output / Work input) x 100%
In the first example, you would need to know the weight of the worker in order to calculate the force output.
In the second example, the actual mechanical advantage of the pulley system needs to be known.
In the third example, the force needed to lift the load is given as 120 N, so that can be used as the force output.