You have three identical, uniform, square pieces of wood, each with
side length L. You stack the three pieces of wood at the edge of
the horizontal top of a table. The first block extends a distance L/4
past the edge of the table. The next block extends a distance L/4
past the edge of the first block, so a distance L/2 past the edge of
the table. The third block extends a distance L/4 past the edge of
the block beneath it, so 3L/4 past the edge of the table. The stack
is unstable if the center of mass of the stack extends beyond the
edge of the table.