Mechanical weight scale working principle:
Figure 1: Beam balance scale
A weighing scale is a device to measure weight. The original form of a weighing scale consisted of a beam with a fulcrum at its center. To determine the weight of a certain object, a combination of reference weights was hung on one end of the beam while the unknown weight object was hung on the other end. For a better or precise work, the center beam balance is still one of the most accurate technologies available, and is commonly used for calibrating and measuring the weight of an object.
An example of the working principle of weighing scale is a beam balance scale (Figure 1). The beam balance is a first order lever with fulcrum in the middle while two pans were at the end of each side of the beam balance. An object is placed on one of the pan, to make sure the beam is balance, the same amount of weight were put on the other end of the pan. When an object was place on one of the pan, a gravitational force will act on the pan, F=mg, which makes the pan goes downward because of the force exerted on the pan. And when the other end of the pan were added the same amount of force, F2, the pan with the object will rises and the beam will be balance because the exerted force have been equal. This is represented in the form of equation, F1 = F2, where F1 is the force exerted by the object and F2 is the force exerted to make the pan balance. The amount of force exerted to make the beam balance is the weight of the object measured.