1. I used the center of gravity point of demonstration balance as fulcrum (pivot).
2. I suspended the given unknown mass object and other three different masses by means of a hook on each side of the fulcrum on the demonstration balance. Then I adjusted the distances and masses of three different masses, so it mean that the demonstration balance was in horizontal position and at equilibrium condition. There were four forces (weights) on the demonstration balance (three different weights and the weight of unknown mass).
3. Then I recorded the weights of masses and their position in the data table.
4. After that I have to found the lever arm for each of the weight.
5. From the observations of anti-clockwise torques and clockwise torques, I set up the equation for equilibrium torques.
6. I calculated the unknown mass of the object (M) and wrote down it in data paper.
7. I calculated the weight of unknown mass object.
8. I obtained the mass of unknown mass object by weighing on the laboratory digital scale.
9. I found the percentage error of mass of the object and recorded in data paper.