A hollow spherical body of inner and outer radii 6 cm and 8 cm respectively floats half-submerged in water. Find the density of the material of the sphere.
The volume of the sphere immersed is equal to the half of the volume of the spherical shell of radius 8cm.
Therefore, volume immersed, 
Mass of the water displaced, 
—————(1)
Volume of the body, 
Let the density of the material be 
.
Mass of the material, 
—————(2)
The buoyant force is equal to the weight of the water displaced and is also equal to the weight of the body.
Therefore, equating (1) and (2)
The density of the body is 
.
1