Archimedes principle

Question

A spring scale calibrated in kilograms is used to determine the density of a rock specimen. The
reading on the spring scale is 0.45 kg when the specimen is suspended in air and 0.36 kg when
the specimen is fully submerged in water. If the density of water is 1000 kg/m3, what is the
density of the rock specimen?

Answer 1

Mass of water displaced is calculated by finding the difference between the actual and apparent masses

This has a value of 0.45kg - 0.36kg = 0.09kg

The rock and water that is displaced have exactly the same volume and thus their densities is the same. This makes the ratio of their masses to be the same

Ratio of masses is

0.45 / 0.09 = 5.0

Here we can see that the mass of the rock is five times the mass of the water so it must be five times denser

Thus, since the density of water is 1000 kg/m³ , the density of rock is 5000 kg/m³