A certain block weighs 15N in air. But it weighs only 12N when completely immersed in water. When immersed in another liquid, it weighs 13N. Calculate the relative density of (1) the block and (ii) the liquid.

Explanation

(i)`RD_(B)-=(rho_(b))/(rhoH_(2)O)=(rho_(b)V_(b)g)/(B_(H_(2))O)=(W_(air))/(W_(air)-W_(H_(2))O)`:Where `W_(air)`=15N (weight of the body in air) and `WH_(2)O=12N` (weight of the body in water)
`there R.D_(B)=(15N)/(15N-12N)=5`
(ii)`(rho_(b))/(rho_(L))=(rho_(b)V_(B)g)/(rho_(L)V_(B)g)=(m_(B)g)/(B_(L))=(W_(air))/(W_(air)-W_(L))` where `W_(L)`=13N (weight of the body in liquid)
`therefore (rho_(b))/(rho_(L))=(R.D_(B))/(R.D_(L))=(15N)/(15N-13N)=(15N)/(2N)therefore R.D_(L)=(2)/(3)`