Balance Scales

Balance scales are composed of a two-armed lever (balance beam) with equally long arms. Weighing pans at the end of both arms are used to position the weighted object (on one side) and reference masses (on the other side). The balance beam has a vertical tab in the middle, a pointer, which allows you to accurately read when both parties are in balance. The accuracy and sensitivity of the weights requires that the fulcrum is essentially friction-free (a knife edge is the traditional solution). Arrestment device allows lever to lift from the blade and immobilize the scales. Balance scales are simple device and if the suspension of lever is well-designed, they are also very sensitive. The disadvantages of balance scales are sensitivity to shocks and the need for a set of masses. Scales are in equilibrium if the torque forces on both sides are of the same size. If the force is bigger on one side, the balance scales overbalance.