Additional Info

• ID Code: B1-18
• Purpose: To demonstrate how an object's behaviour can change when its center of mass does
• Description: An empty soda can can sit upright on its bottom, or can be laid on its side, but cannot be at rest at any angle between these. However, this can be changed by adding a liquid to the system. Pour approximately 150ml of water into the can, and then try carefully balancing the can at an angle, as seen in the photo above. (This may require experimenting to find the exact right amount of water for any given can; we recommend doing this in front of the class so they can see the process.)

  Ask your students why this should happen? The mass has increased, but why does that change how it balances?

  The water moves when the can tilts, causing the center of mass to shift – with just the right amount of water, the new center of mass will be above the edge of the can, and so it will balance.

  Some cans will tend towards a particular orientation and will roll along the edge to that point, displaying a damped oscillation – invite students to hypothesize why this is.

• Availability: Available