# Homework Help: Buoyancy with Water and Oil

1. Jan 22, 2009

### laurenh19

i have a physics problem about buoyancy and could really use some help!
a cubical block of wood 10cm on a side, floats at the interface between oil and water with the lower surface 2cm below the interface. the density of oil is 0.6 g/cm^3 and the density of water is 1.00g/cm^3. what is the mass of the block?
it also has a picture that shows that the container is filled with 10cm of oil on top of 10 cm of water.

force=(density)(volume)(gravity)

i have no idea where to even begin!

2. Jan 22, 2009

If half the volume of the block was below the boundary (5cm below) the block would have a density half way between that of oil and water (i.e 0.8 g/cm^3). From the density you could easily calculate the mass, try using the same argument for the numbers in your question.

3. Jan 22, 2009

### laurenh19

i'm confused on why they would say that the container is 10cm full with oil and 10 cm full with water...do i have to add that into my calculations somewhere?

so far ive come up with

mass=(0.6g/cm3)(8cm)+(1.00g/cm3)(2cm)