Bouyant force with water and in equilibrium

[bdh2991]

Homework Statement

A cube of wood having an edge dimension of 20.9 cm and a density of 651 kg/m3 floats on water.

what is the distance between the top of the cube to the water level?

Homework Equations

F = density*g*Volume

The Attempt at a Solution

I believe i have the right concept down in which i did the sum of the forces so it would be:

-(density of cube*g*V_total) + (density of water*g*V_displaced) = 0

I would like someone to confirm this for me and i also wanted to ask...couldn't i just use mg for the force of the cube downward and then add the buoyant force of water to it? (if not then why not?)

for example: -m_cube*g + (density of water*g*V_displaced)

 

[bdh2991]

nvm...i complete forgot that d = m/v, therefor the force due to gravity is the same for mg or density*g*volume...sorry about that

 

[SteamKing]

Hint: check out Archimedes principle.