Concept:A beam balance works by comparing moments of forces on both sides of its fulcrum.
Explanation:When the beam is horizontal and balanced, the clockwise moment equals the anticlockwise moment.
Moment is the product of force and perpendicular distance from the pivot.
The unknown weight on one pan produces a moment balanced by standard weights on the other pan.
Therefore, a beam balance directly applies the principle of moments.
Hooke’s law relates to springs, while Archimedes’ principle and the law of flotation relate to fluids and buoyancy.
So the correct option is based on moments, not the other laws.
Answer:D. principle of moments