Figure 5: Three Blocks Stacked
Let's add a third block between the table and the first two blocks. To do this, we'll position the original two blocks atop the third block exactly as they were positioned on the table-one quarter of the way off. We'll position the third block one sixth of the way off of the table.
The top two blocks are still perfectly balanced atop the third block. But what about the third block? Can you compute the location of the center of gravity of the third block?
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Once again, the center of gravity of the third block is exactly zero, meaning that it is exactly balanced.