# Weird bouyancy/mass/density problem

1. Jun 15, 2010

### cubejunkies

So I'm doing a summer homework assignment for AP Chem and I took normal honors chem last year so I know terminology and things like that, but this question in the summer homework assignment for AP Chem that I've been working on in the review-ish section of the book is not making any sense. I have no idea where to start with this problem. Even though its in a chem book, it seems like a physics question, however, which is why im posting it here. The problem is as follows:

"A student is given a crucible and asked to prove whether it is made of pure platinum. She first weighs the crucible in air and then weighs it suspended in water (density = 0.9986 g/mL). The readings are 860.2 g and 820.2 g, respectively. Based on these measurements and given that the density of platinum is 21.45 g/cm^3, what should her conclusion be? (Hint: An object suspended in a fluid is bouyed up by the mass of the fluid displaced by the object. Neglect the bouyance of air.)"

Sorry if this is a really stupid question to ask and if the solution should be obvious

Anthony

2. Jun 15, 2010

### ehild

Apply Archimedes' principle. How is the buoyant force related to the volume of the crucible and the density of water?

ehild

3. Jun 15, 2010

### cubejunkies

I honestly have no idea :(

4. Jun 16, 2010