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How to Figure Out How Much Something Weighs Without Using a Scale

You can find the weight of something, be it an object or a person, without using a scale. You can do it as a math experiment for fun, or simply because you need to know the weight and don’t have a scale handy. One of the methods is an illustration of the Archimedes Principle, one of the foundations of mathematics, in which the Greek scientist Archimedes realized that the water displaced when he sat in his bath must be equal to his mass, or weight.

Things You'll Need

  • Bathtub
  • Water
  • Object
  • Duct tape
  • Gallon bucket
  • Large container
  • Cube
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Instructions

  1. Displacement

    • 1

      Half fill a bathtub with water and leave the water to settle.

    • 2

      Cut two lengths of duct tape and stick them along the inside of the bath, with the bottom of the tape marking the level of the water.

    • 3

      Place the object in the water and let the water settle again; the water level in the tub will be higher, above the level of the duct tape.

    • 4

      Fill a gallon bucket to the gallon mark with water from the bathtub and pour into a large container. Keep refilling and emptying the bucket until the water level in the tub is where it was before you put the object in the tub, that is, at the bottom of the duct tape.

    • 5

      Note how many gallons of water you took from the bathtub and multiply the figure by 8.34 – the weight in pounds of a gallon of water. This will give you the weight of the object in the bathtub.

    Calculation

    • 6

      Determine the weight of something by using an equation to find the answer. If it’s water, for instance, you can use the formula of density multiplied by volume to find the mass, or weight, of the water.

    • 7

      Take an empty cube that’s 10 x 10 x 10 centimeters. Fill completely with water, then empty the water into a large container. Refill the cube, then discard the water until you’ve used all the water you need to weigh.

    • 8

      Determine the volume of the cube by multiplying 10 x 10 x 10 to come up with 1000 cubic centimeters. Multiply this by the density of the water, which is one gram per cubic centimeter, so for each filled cube you have a weight of 1000 grams, or 35.27 ounces. Multiply this figure by the number of filled cubes, then divide by 16 to establish the weight in pounds and ounces.

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