# Archimedes's Principle Lab

1. Nov 23, 2008

### TURBANator

we were doing a lab to test archimedes's principle and it said to measure the specific gravity of a sphere using a jolly balance..

however, i fail to see how this is related to archimedes's principle since the jolly balance doesnt measure the displacement of the water or its weight..?

what were doing is comparing the specific gravity of an object by taking its density (we measured mass and volume) and dividing it by 1 since thats the density of water.. and the specific gravity of the same object by looking at spring elongation on the jolly balance when not submerged and then fully submerged in water..

can someone explain to me why were comparing specific gravity when archimedes's principle is about buoyant force? thanks! : )

btw, i think i posted this in the wrong place, haha. sorry, can a mod move it?

Last edited: Nov 23, 2008
2. Nov 24, 2008

### tiny-tim

Welcome to PF!

Hi TURBANator! Welcome to PF!

You measured the volume before you used the jolly balance.

The jolly balance measures the buoyant force by subtracting the ordinary weight from the submerged weight.

So you compare the buoyant force with the volume to check whether Archimedes was right!

3. Nov 24, 2008

### Savant13

Now I'm not sure what a Jolly Balance is, but I can help with the equations.

The Bouyant force is equal to gravity times density of the fluid times displaced volume.

B=gDV

V=B/gD

Then you get the density of the submerged object by taking its mass and dividing by the calculated volume