# How far a cube sinks below the waterlevel

#### justinram22

1. The problem statement, all variables and given/known data
A wood cube .30m on each side has a density of 700 kg/m^3 and floats levelly in water. (a) What is the distance from the top of the wood to the water surface? (b) What mass has to be placed on top of the wood so that its top is just at the water level.

2. Relevant equations
I assume the buoyancy equation.

3. The attempt at a solution
I figured out part (a) no problem, but seem to be having difficulty with part (b).

I assume it has to be:
Density=(mass/volume)?
When i do that I get 18.9, where the back of the book says 8.9

Thanks guys so much! Hope once I actually get good at physics I can come back and help people similar to myself!!

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#### SammyS

Staff Emeritus
Homework Helper
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How much would the wooden block weigh if its density was the same as the density of water?

#### justinram22

Sorry, but I'm still lost?

So

1000=(mass/.027)
mass=27?

Thanks!!

Staff Emeritus
Homework Helper
Gold Member
27 what?

#### justinram22

27kg

Which is not what they had in the back of the book (they had 8.9).

Thanks You again!

#### SammyS

Staff Emeritus
Homework Helper
Gold Member
How much does a cube of water weigh which is 0.30 m on each side?

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