A block of wood floats in a liquid with four-fifths of its volume submerged. If the relative density of wood is 0.8, what is the the density of the liquid in units of kg m-3?
Let the volume of the block be .
Volume of block under liquid
Volume of liquid displaced
Now let the density of the liquid be .
Mass of liquid displaced
= (volume of liquid displaced) x (density of liquid)
Weight of liquid displaced
Relative density of wood = 0.8
Density of wood
Mass of the block
Weight of the block
From the law of flotation,
Weight of block = weight of liquid displaced