An elegant experiment in mechanical equilibrium

Abstract

The authors present an experiment on the second condition of mechanical equilibrium. The first condition of mechanical equilibrium is that the vector sum of all forces acting on an object should be 0. The second condition is simply the ancient law of levers which was known to Archimedes. For a body in mechanical equilibrium the net torque taken with respect to any axis must also vanish. They begin by considering a weightless triangle V1V2V3. By triangle they mean the boundary of the triangle together with its interior. The purpose of the experiment is to use the second condition of mechanical equilibrium to locate the point of concurrence of the three angle bisectors in an arbitrary triangle. Since each angle bisector is equidistant from the sides of its angle, the point of common to all three bisectors must also be the centre of the inscribed circle.