Physics
posted by Lindsey .
A cube of oak with sides 15cm long floats upright in water with 10.5cm of its depth submerged. What is the density of the oak?

The weight of the oak equals the weight of a 15 x 15 x 10.5 cm block filled with water (since that is the buoyancy force). That is the displaced volume of water.
The density of the block is
(water density)x(15 x 15 x 10.5)/(15 x 15 x 15) = 1 x 10.5/15
= 0.70 gm/cm^3 
Part inside = 10.5 /15
And inside also equal to d1/d2
And u get the answer 0.70
G/cm3