Answer:
Some work input is lost to friction
Explanation:
The efficiency of a machine is defined as:
[tex]\eta = \frac{W_{out}}{W_{in}}[/tex] (1)
where
[tex]W_{out}[/tex] is the work output
[tex]W_{in}[/tex] is the work input
Due to the law of conservation of energy, the work output can never be larger than the work input (because energy cannot be created). Moreover, in real machines part of the work input is lost due to the presence of frictions: as a result, part of the energy in input is converted into thermal energy or other forms of energy, and so the work output is smaller than the work input, and so the ratio (1) becomes less than 1, and so the efficiency is less than 100%.
