# Homework Help: Buoyant Force

1. Jan 17, 2012

### kswoff

So I'm in a general physics class and the teacher asked us to find the percentage of a sphere immerses in water and I can't seem to figure out how to find the percentage. I was wondering if there's an equation to use or what to find the answer. Thanks.

2. Jan 17, 2012

### Simon Bridge

Welcome to PF.
When you get stuck like this, try thinking of a similar situation you do know the answer to.

Hint: you know ice floats approximately 90% submerged? (nine-tenths)

What is the density of ice divided by the density of liquid water?
What is that as a percentage?

3. Jan 17, 2012

### kswoff

Okay that makes sense. In this same question, it asks to draw a free body diagram to find all the forces. I only found the buoyant force and the gravity force and those don't allow me to have two densities. So did I do the FBD wrong and I'm missing some forces or do I rearrange archimedes' principle to substitute another density? Hope this makes sense.

4. Jan 17, 2012

### Simon Bridge

Is the buoyant force related to the densities?

5. Jan 17, 2012

### kswoff

I'm assuming so that way I can solve for the percentage.

6. Jan 18, 2012

### Simon Bridge

So if you have a buoyant force in your free body diagram, that accounts for the two densities right?