Take a 355 ml can and fill it with water, about a third of its volume. Then tilt it on its rounded bottom edge. It must then remain in balance. Finally, lightly push the top of the can to make it turn on itself. Impressive, isn’t it?
Tell the children that sometimes some things seem impossible to us. “But how will this happen?” God always has a way of doing things, which at first escapes us. But if we trust him, anything is possible!
If the can is empty, it cannot be held in an inclined position, it falls systematically. Similarly, when it is full. The “trick” is to put the right amount of water so that there is so much water on either side of the vertical rotation axis that passes through the point on which the can balances. The water that is added to the can is a weight. In order for the can to hold in balance, this weight must be evenly distributed, just like the balance of a scale, and it is only in this condition that the center of gravity of the can is located on the vertical rotation axis. As soon as the weight is not evenly distributed, the center of gravity of the can is no longer located on this axis, and the can falls.