A vessel contains oil (density `= 0.8 g//cm^(3)`) over mercury (density `= 13.6 g//cm^(3)`). A uniform sphere floats with half its volume immersed in mercury and the other half in oil. The density of the material of sphere in `g//cm^(3)` is

Options

A. 3.3
B. 6.4
C. 7.2
D. 12.8

Answer

C

Explanation

Weight of sphere = Upthrust due to Hg + Upthrust due to oil,
i.e. `Vdg=(V)/(2)d_(Hg)g+(V)/(2)d_(oil)xxg`
`rArrd=(d_(Hg)+d_(oil))/(2)=(13.6+0.8)/(2)=7.2g//cm^(3)`