Science Buddies: "Ask an Expert"

My 10 year old son is doing the "Archimedes Squeeze" science experiment from your web site. He is also doing the additional testing under the "make it your own" tab, but we are having a difficult time answering the question "For each diameter of the sphere, what is the mass of the water that was displaced?" Is there a formula for this mass of water displacement based on the percentage of the sphere that is submerged? He found a formula where the fraction submerged is equal to the ratio of the volume of the sphere submerged to the volume of the sphere:
fraction submerged = V submerged divided by V of object and then the volume submerged is equal to the volume of the fluid displaced
but we are having a hard time correlating this to the mass of water displaced. Do you have to plug the volume of the fluid displaced into the density of water to determine the mass?
I feel like this is becoming way too complicated and we are missing bleep simple.
Any help you can offer would be very much appreciated.

Hello and welcome to the forums:

It sounds like you've figured out the answer - yes, you have to use the density of water to figure out the mass of water displaced. Fortunately, in the metric system, we can use 1g / ml as the water density for most cases. That means that the volume you calculate, in cubic centimeters, is equal to the number of grams displaced (1 cc = 1 ml). Isn't the metric system great!

Please let us know how the experiment turns out and if you have any other questions.
Best, Keith