The most common way to measure mass is using a mass balance scale. A balance scale compares the mass of an unknown object to the mass of a known object. An advanced, calibrated mass balance scales can measure an object's exact mass. But a simple, homemade balance scale can also give a good estimate.
Find the exact centre of the ruler. Drill a small hole in the exact centre. Place the ruler horizontally and drill two more holes above the first. The holes should be drilled in a straight line. These holes should be at exactly the 6-inch mark on the ruler.
Drill two holes near the ends of the ruler. These holes must be equidistant from the centre hole and horizontally aligned with the centre hole. The vertical holes should make a straight line down the vertical centre of the ruler and the horizontal ray of lines should divide the ruler horizontally
Bend the three paper clips into hooks and insert two into the holes near the end of the ruler and one in the middle hole at the centre of the ruler. The centre paper clip will hang from a string, nail or something else on which it can rotate. Consider this and bend the paper clips accordingly. The paper clips at the end of the rulers should have hooks bent into them at the bottom. These hooks will hold strings that will attach to the cups.
Poke two small holes in each cup near the top and directly opposite each other. Cut two pieces of string the same length. Tie the ends of one string to the holes in a cup. Do the same to the next cup.
Hang the cups from the outer paper clips by the strings. Hang the ruler from a supported string, long nail or something else that can hold the middle paper clip and allow it to rotate back and forth.
Use the balance scale. This simple balance scale will not give exact mass measurements. Use a common object to compare masses to. Pennies are often used in simple mass balance scales because their mass is known to be about 2.6 grams. Place a small object in one cup and add pennies to the other cup until the scale is balanced. Multiply the amount of pennies by 2.6 grams. This is the approximate mass of the object.