An object weighs 50g in air and 12g in water. Find the density of the object.
Solution
From Archimedes principle :
Weight of object in water is given by,
( ρs - ρw )Vg = 12 ...1)
Where ρs is density of solid, ρw is density of water and V is volume.
Weight of object in air is given by,
ρsVg = 50 ...2)
Buoyant force of air is taken as negligible.
Dividing 2) by 1) we get
25ρs - 25ρw = 6ρs
19ρs = 25ρw
Since density of water is 1000 kg/m3
ρs = ( 25/19 ) x 1000
ρs = 1.316 x 1000
ρs = 1316 kg/m3
From Archimedes principle :
Weight of object in water is given by,
( ρs - ρw )Vg = 12 ...1)
Where ρs is density of solid, ρw is density of water and V is volume.
Weight of object in air is given by,
ρsVg = 50 ...2)
Buoyant force of air is taken as negligible.
Dividing 2) by 1) we get
25ρs - 25ρw = 6ρs
19ρs = 25ρw
Since density of water is 1000 kg/m3
ρs = ( 25/19 ) x 1000
ρs = 1.316 x 1000
ρs = 1316 kg/m3