Archimedes' Principle and Density Determination
Archimedes’ Principle: The Method of Hydrostatic Weighing
Archimedes’ Principle aids in the determination of density by providing a convenient and accurate method for determining the volume of an irregularly shaped object, like a rock. This method is quite commonly used in the construction industry.
It is known also as Hydrostatic Weighing.
Example:
P = Density m = Weight or Mass in Air m2 = Weight in Water
An object is weighed in air and found to have mass m = 500 g
It is then submerged in water and found to have apparent mass m2 = 420 g
It is clear that it has displaced m – m2 = 80 g of water. Since water has a density of 1 gram/cm3, this implies:
Volume of object = m2 = 80 cm3
The density of the object is then p = m⁄v = 500⁄80
P = 6.25
Note that with use of a suitable “Below Balance Weighing” device, these measurements are easy to accomplish. The balance will not see the weight of the water, just the effect of the water on the object.
Note: For correct results, the water should be free of contaminants and the temperature of the water is a variable that should be taken into account.
Archimedes’ Principle aids in determining density by providing a convenient and accurate method for determining the volume of an irregularly shaped object, like a rock. This method is commonly used in the construction industry. It is also known as Hydrostatic Weighing.
An Example
P = Density
m = Weight or Mass in Air
m² = Weight in Water
An object is weighed in air and found to have mass, of m = 500 g.
It is then submerged in water and found to have an apparent mass, of m² = 420 g.
It is clear that it has displaced m – m² = 80 g of water. Since water has a density of 1 gram/cm³, this implies:
Volume of object = m² = 80 cm³
The density of the object is then p = m⁄v = 500⁄80
P = 6.25
Other Notes:
Note that with the use of a suitable under-balance weighing device, these measurements are easy to accomplish. The balance will not factor the weight of the water, just the effect of the water on the object.
Note for correct results, the water should be free of contaminants. The temperature of the water is also a variable that should be considered.
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