• Question: Why does a coke can balance on its rim when its 1/3 full?

    Asked by paulfee1 to Cathal, Ciara, Emma, Michael, Sive on 13 Nov 2013.
    • Photo: Cathal Cummins

      Cathal Cummins answered on 13 Nov 2013:

      Let me begin by asking you another question: why does an empty coke can topple over when it is placed on its rim? The answer is that the top part of the can is too heavy and topples the can over. But if you fill the can up 1/3 the way the top part of the can can’t compete with the heavy liquid, which wants to keep the can firmly on the table.

    • Photo: Michael Nolan

      Michael Nolan answered on 20 Nov 2013:

      There must be a perfect balance between gravity wanting to topple the coke can and the weight of the liquid in the can wanting to make it stand upright. You could go a little under or a little over this amount of lquid and see what happens – is an exact amount of liquid needed or can you have a range and still get the balance.

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