Watch the centre of gravity move

Watch the video and listen to the sound.

During the demonstration you will see a balast weight being added to a plastic cup and then sugar being added.

As the sugar is added the cup changes its position in the water.

How does it change? Does it move up or down?

Copy this demonstration and see what happens if you push the top of the plastic cup when it has little sugar in it, and then when it has lots of sugar in it. Which is the more stable - when it is light, or when it is heavy?