Fluid Mechanics?

A cubical block of wood 10.0 cm on a side floats at the interface between oil and water with its lower surface 2.00 cm below the interface. The density of oil is 750 kg per cubic meter. (a) What is the gauge pressure at the upper face of the block? (b) What is the gauge pressure at the lower face of the block? (c) What is the mass of the block?


Height of the oil column = 10 cm


Height of the water column = 10 cm

Fluid Mechanics?
a) Pressure = (2cm of oil) x (750kg/m^3)





b) Pressure = (10cm of oil x 750g/m^3) + (2cm of H2O x 1.00g/cm^3)





c) Mass of the block = Rho block x Volume block





Rho block = Rho water - 4/5(Rho water - Rho oil)





and





Rho Block = Rho oil + 1/5(Rho water - Rho oil)





Which is (Choose one. I'll do both):





1.00g/cm^3 - 4/5(1.00g/cm^3 - 0.75g/cm^3)





1.00g/cm^3 - 0.2g/cm^3 = 0.8g/cm^3





or





0.75g/cm^3 + 1/5(1.00g/cm^3 - 0.75g/cm^3)





0.75g/cm^3 + 0.05g/cm^3 = 0.8g/cm^3





Either way you get 0.8g/cm^3





Mass = Density x Volume





Mass = 0.8g/cm^3 x 1000cm^3





Mass of block = 800 grams
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