# Displacement and mass of water in a column [duplicate]

I attempted to modify a classic experiment to demonstrate Archimedes principle to my 5th graders and I created an error I can’t explain.

We started with a graduated cylinder containing 20 mL of water. We added 10 pennies to the cylinder forcing a rise of about 5 mL to the column, or a total of 25 mL We then placed the 10 pennies into one pan of a balance We the used a syringe to place 5 mL of water on the other side of the balance

At this point I was ready to scream Eureka and have them bask in the equivalence of the displaced water to the object(s) that caused the displacement.

Unfortunately, the two masses were no where near equal... no Eureka. The 5 mL of displaced water in the cylinder was not equal to the mass of the 10 pennies I had the kids keep adding water until it balanced and it was about 25 mL to match the mass of 10 pennies

I have seen this video experiment before using an overflow vessel and watched countless online professors show the mass of the displaced water equal to the mass of the object.

Yet for some reason that I can’t explain I could t get this to work when you measure the displacement in a cylinder

Anyone have any ideas on what kind of obvious error in thinking and / or procedure am I making here?

Thanks

## marked as duplicate by sammy gerbil, Community♦Nov 28 '17 at 2:46

• Sure the videos you saw didn't involve floating objects? – DJohnM Nov 28 '17 at 0:35
• Some of them were floating but some were steel cylinders submerged in an overflow vessel. I even saw a science teacher climb into a huge full tub of water and measure the overflow. I figured displacement is displacement whether object sinks or floats. – tyroneaphone Nov 28 '17 at 1:03
• Your error is having an incorrect idea about what Archimedes' Principle actually states. Check your sources of information. Look at those videos again. – sammy gerbil Nov 28 '17 at 1:15