Answer:
Functions of counterweight :-
1. A weight used as a counterbalance.
2. A force or influence equally counteracting another
In theory ( ideal ) a counterweight means that a system has NO net forces due to gravity and is balanced with no tendancy to move even tho' free to do so.
This means a separate force applied does not have to do gravitational work ( lifting ) but only against friction . So for example if I suspend two 1 ton weights over a rope and pulley , which are balanced, then to move them does not require me to lift 1 or 2 tons . They still have inertia ( and resist moving ) but not due to weight , and if there is little friction then any applied force would move them but slowly if the force applied was small.