# Homework Help: Buoyant Pressure problem number 7

1. Nov 13, 2011

### ChunkymonkeyI

1. The problem statement, all variables and given/known data
When a beaker partially filled with water is placed on an accurate scale the scale reads 22.0g. If a piece of wood with a density of 0.905 kg/dm^3 and volume of 2.10 cm^3 is floating on the water, what will the scale read

2. Relevant equations
m=Density times volume

3. The attempt at a solution
m=density times volume
m=1000 kg/m^3 times 2.1 times 10^-8 m^3
m=2.1 times 10^-8 g
and when I add that to 22.0 g i still get 22.0 g but the answer should be 23.9 g and idk what I'm doing wrong. maybe I didn't account for the object floating on water or something like that so can someone please help me

2. Nov 14, 2011

### BruceW

the mass of the wood is just the density of the wood times the volume of the wood.

I think 22g means the mass of the beaker & water (in grammes). So all you need to do is add the mass of the wood to this mass to get the total mass which the scale will read.

Be careful with the dm and cm units.