How far a cube sinks below the waterlevel

[justinram22]

Homework Statement

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.

Homework Equations

I assume the buoyancy equation.

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!

 

[SammyS]

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!

 

[SammyS]

27 what?

 

[justinram22]

27kg

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

Thanks You again!

 

[SammyS]

How much does a cube of water weigh which is 0.30 m on each side?