You can measure the weight of an object using water through the principle of water displacement. This method leverages Archimedes' principle, which states that the buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by the object.
The Water Displacement Method
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Prepare a container: Use a container with a known volume marking (e.g., a graduated cylinder or a measuring cup) and fill it with a known amount of water. Record the initial water level precisely.
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Submerge the object: Carefully submerge the object whose weight you want to measure into the container. Ensure the object is fully submerged but does not overflow the container.
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Measure the new water level: Note the new water level after the object is submerged. The difference between the initial and final water levels represents the volume of water displaced by the object.
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Calculate the weight: Since the weight of the displaced water is equal to the weight of the object (Archimedes' principle), you can determine the object's weight by calculating the mass of the displaced water and then converting the mass to weight using the acceleration due to gravity (approximately 9.8 m/s²). Knowing the density of water (approximately 1 g/mL or 1 kg/L), and having determined the volume of displaced water, the mass, and therefore the weight, can be readily calculated.
Example:
- Initial water level: 50 mL
- Final water level after submerging object: 75 mL
- Volume of water displaced: 75 mL - 50 mL = 25 mL = 25 cm³ = 0.025 L
- Density of water: 1 g/mL or 1 kg/L
- Mass of displaced water: 0.025 L * 1 kg/L = 0.025 kg
- Weight of displaced water (and therefore the object): 0.025 kg * 9.8 m/s² ≈ 0.245 N (Newtons)
This method is particularly useful for determining the weight of irregularly shaped objects where traditional weighing methods might be difficult. It's crucial to ensure that the object is completely submerged and that no air bubbles are trapped, as this can affect the accuracy of the measurement. The reference materials highlight this by stating that "the increase in weight of the water level volumes will equal the weight of the object."
