# Help with a buoyancy problem?

1. Jun 5, 2005

### psycovic23

"A solid wooden cube, 30.0cm on each edge, can be totally submerged in water if it is pushed downward with a force of 54.0N. What is the density of the wood?"

I know so far that the buoyant force would equal the 54N, but I don't know how to get the mass of the cube to determine the density. Can you help?

2. Jun 5, 2005

### Dr.Brain

So the cube completely submerges into water...

Downward Force + Weight = Buoyant Upward Force

Solve as per above...Show your work..

3. Jun 5, 2005

### HallsofIvy

No, you don't know the bouyancy force is 54 N! How much would a cube of water, 30 cm on a side, weigh? That's the bouyancy force pushing the wood upward. The weight of the cube, plus the 54N pressing it down must equal that. Set up that equation and you can solve for the weight of the cube of wood.

4. Jun 5, 2005

### Dr.Brain

Buoyant Force= Density of water x Volume of cube x g

Why the full volume of cube?...

Weight of cube = density of cube x Volume of cube x g

Can you solve further?

5. Jun 5, 2005

### psycovic23

Ah...800kg/m^3! Thank you!