PHYSICS [2 Mark Question Answer]

If a machine is 70% efficient, it means that 70% of the work input to the machine is obtained as the useful work output.
The remaining 30% of the work input has been lost in overcoming the friction and other factors.

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.

The principle of an Ideal Machine:
It is defined as a machine that converts all the input energy into useful output energy. The efficiency of the ideal machine is 100%.
The principle of the ideal machine is that the work done by the machine is equal to the work done on the machine..

Machines are used to :
Change the effort in the desired direction.
Speed up the motion of a body.
Lift a heavy load by applying a small effort.
Do unsafe and dangerous work.