Question

Define the term efficiency of a machine. Give two reasons for a machine not to be $100\%$ efficient?

Answer 1

The efficiency of a machine indicates how well its input energy is converted to useful output energy or work. It is a major factor in the usefulness of a machine and is the fraction or percentage of the output divided by the input.

It is the ratio of the useful work done by the machine to the work put into the machine by the effort.
In the actual machine, there is always some loss of energy due to
1)friction and
2)weight of moving parts,
thus the output energy is always less than the input energy.