Parts of a Balance Scale

Every object has a certain weight and mass. The weight of an object is proportionate to gravitational force that pulls the matter and the mass is the amount of matter in an object. While weight fluctuates according to gravity, the mass is always the same. Spring scales can only determine the weight of an object, while balance scales always measure its mass.

Identification

A balance scale is a device used to determine the mass of an object. It is the first scale invented and it uses standard masses (also known as weights) to determine the unknown mass of an object. The balance scale is considered the most accurate scale. A balance consists of a weighting platform, device platform and a beam.

How It Works

The object of unknown mass is placed in one of the weighting platform's pans. In the other pan, the standard weights are placed.To determine the object's mass, the beam needs to be as close to equilibrium as possible. If one of the sides is heavier, the lighter pan is raised up and the heavier pan is lowered. The object's mass is equal to the sum of the standard weights that are in the pan when the beam is in equilibrium. Dust and air currents can affect the balance's operation.

Weighting Platform

The weighting platform, as the name suggests it, is the part of the scale that holds the object that needs to be measured and the standard weights. It consists of two pans of identical weights and stirrups. The pan is a round plate, usually made of metal, in which the measured object and weights are placed. The size of the pan limits the size of the objects the balance can measure. The stirrups hold the pans and connect them to the beam. The stirrup is usually a wire or strip of metal.

Device Platform

The device platform consists of a base and a central pillar. The base has leveling screws that allow the user to level the scale. For example: if the scale is placed on a surface that is not perfectly horizontal, turning one of the screws will allow the balance to be leveled. The central pillar rests on the base and is connected to it through an arresting screw that supports it. By turning the arresting screw, the beam that rests on top of the central pillar is raised or lowered.

Beam

The beam is a horizontal lever of equal length arms that rests on the central pillar. From each arm of the beam, the pans are suspended. When one of the pans tilts the beam on one side, even though the weight of the pans is identical, the balance screws attached to the beam allow the user to put the beam in equilibrium. The balancing screws can be moved from one side of the beam to the other, bringing the beam in horizontal position.

References

• Balance Scale Usage
• Mass and Weight

Resources

• Common Balance