Balance Scale

4 (e) explain that weights, and therefore masses, may be compared using a balance.

A balance is a measuring instrument used to measure the mass and weight of a body. It works on the principle of moments, which will be elaborated later. The beam is balanced, or let us say it becomes straight when the masses in both pans are of the same value. The following image is the simplest form of a balance.

In one pan of the balance, we put an object of a known mass. In the other pan, the object with the

unknown mass is placed. Gradually the mass in the first pan is either increased or decreased with the addition of objects of known masses until the beam is balanced. Once the beam is balanced, we know that the mass of the objects on both side is equal

Let us take an example. We want to know the mass of a rock. We put it in the left pan of the balance. Now, to balance the beam, we will gradually put objects of known masses in the other pan. If the beam becomes balanced when the total mass of the objects in the second plate is lets say, 2 Kg, we will know that the mass of the rock is 2 Kg.

Weight and Mass

We know that weight depends on gravitational force, while mass is an independent quantity. A balance is used to measure the mass of an object. It does so by comparing the masses of two different objects. As a result, whether a balance is used on Earth, or on Moon, it would give us the same values of masses.

Furthermore, we can calculate the weight of an object once we have calculated the mass by using the equation W = mg, where m stands for mass and g stands for gravitational force in that area.

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