Step-by-step in­struc­tions 

If you try to bal­ance an emp­ty or full can at an an­gle, you’ll find that you can’t. The can’s cen­ter of mass pro­jec­tion ex­tends be­yond the bound­aries formed by the two sup­port points.

Process de­scrip­tion

“Cen­ter of mass” is a point char­ac­ter­iz­ing the move­ment of an ob­ject or sys­tem of ob­jects as a whole. An ob­ject al­ways strives to oc­cu­py a po­si­tion where its cen­ter of mass is low­er. A can rests solid­ly on a ta­ble and is in sta­ble equi­lib­ri­um if the hy­po­thet­i­cal ver­ti­cal line that can be drawn through its cen­ter of mass falls be­tween its ful­crum points. If this is not the case, the can will fall. The can’s cen­ter of mass shifts with the ad­di­tion of wa­ter. If the wa­ter lev­el is such that the pro­jec­tion of the can’s cen­ter of mass falls be­tween its sup­port points, then the can won’t fall.