Mechanical weight scale working principle:
Figure 1: Beam balance scale
A weighing scale is a device to measure weight or mass. The original form of a weighing scale consisted of a beam with a fulcrum at its center. To determine the mass of a certain object, a combination of reference weights was hung on one end of the beam while the unknown mass 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 mass of test weights.
An example of the working principle of weighing scale is a balance beam 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 mass 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 mass balance.