# Wood Floating on Water (1 Viewer)

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#### littlkj5

1. The problem statement, all variables and given/known data

A block of wood of uniform density floats so that exactly half of its volume is underwater. The density of water is 1000 kg/m3. What is the density of the block?

2. Relevant equations

3. The attempt at a solution

I tried 500 kg/m3 divided by 1000 kg/m3

#### Chi Meson

Homework Helper
Why did you divide the density of the block by the density of water? What did that get you?

#### littlkj5

I found that the density equation was Density=Mass/Volume.

#### emg333

I think you use Archimedies ' principle for this= the buoyant force on an immersed object has the same magnitude as the weight of the fluid displaced by the object.

#### littlkj5

so which equation would that be?

#### Chi Meson

Homework Helper
I tried 500 kg/m3 divided by 1000 kg/m3
Chi Meson said:
Why did you divide the density of the block by the density of water? What did that get you?
I found that the density equation was Density=Mass/Volume.
Density = m/V, but that is NOT what you did above. You divided the "density of the block of wood" over "the density of water." THAT is what (500 kg/m^3)/(1000 kg/m^3) is. First of all, what made you pick "500 kg/m^3" anyway? It's not given information. It is in fact the answer to the question, but it appears to be accidental. Again my question is, why did you make that division?

#### littlkj5

I did this because it said half of its volume is underwater so therefore I assume it was 500. So then I did the division. I guess I over thought the question. More than what was needed.

#### Chi Meson

Homework Helper
You still might need to explain why a density that is half of water will be half-submerged. Find Archimedes' principle and read it aloud. You also should understand that the division you did is NOT the same as the formula you stated.

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