I found this problem in ‘200 puzzling physics problems’
- An empty cylindrical beaker of mass 100 g, radius 30 mm and negligible wall thickness, has its center of gravity 100 mm above its base. To what depth should it be filled with water so as to make it as stable as possible?
Well, I solved it but want to understand the answer: why must the center of mass always lie on the water surface for maximum stability?
In the solution given in this book, it explains that the height of center of gravity would increase on filling more water after acquiring the condition of the center of mass lying on water surface but does not explain why the center of mass cannot be below it.