A cubical block of wood of specific gravity `0.5` and chunk of concrete of specific gravity `2.5` are fastened together. the ratio of mass of wood to the mass of concrete which makes the combination to float with entire volume of the combination submerged in water is

Options

A. `1//5`
B. `1//3`
C. `3//5`
D. `2//3`

Answer

C

Explanation

W=Upthrust
or `(m_(1)+m_(2))g=[(m_(1)//0.5xxrho_(w))+(m_(2)//2.5xxrho_(w))]rho_(w)g`
or `m_(1)+m_(2)=2m_(1)+0.4 m_(2)`
or `m_(1)=0.6 m_(2)`
`therefore " " (m_(1))/(m_(2))=0.6=(3)/(5)`