Where is the fulcrum of the scales?
The fulcrum is the point on which the lever rests.
What is the weight?
The weight is the lead put in one scale.
What is the power?
The power is the substance put in the other scale, so as to balance the weight.
When the lead put in one scale weighs exactly a pound, how much sugar must be put in the other scale to balance the lead?
Exactly one pound of sugar must be put in to balance the lead.
For what is a balance mostly used?
A balance is mostly used for weighing heavy bodies.