A stone has mass X in air and displaces volume Y of water. Its density is found by dividing:
Athe mass in air by the upthrust
Bthe reduced mass by the volume displaced
Cthe apparent mass in water by that volume
Dthe mass in air by the volume displaced
Answer & Solution
Correct answer: D. the mass in air by the volume displaced
1. Density is mass divided by volume, and both must refer to the stone itself.
2. The true mass of the stone is its mass in air, before any upthrust acts on it.
3. When fully immersed, the stone displaces its own volume of water.
4. So the volume of water displaced is the stone's volume.
5. Dividing the mass in air by that displaced volume gives the density; using the apparent mass in water subtracts the upthrust and understates it.
_Source: NECTA CSEE 2021 Physics 031, Question 1: Multiple Choice, item (i)_
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