The experiment is the following:
First part - The demonstrator puts an egg in the table, and places a heavy block resting above the egg, then he applies a force in the heavy block using the hammer, and the egg doesn't break.
Second part - Now he takes the heavy block away, and instead places a lighter wooden block, then applies a force with the hammer again, and breaks the egg.
The explanation to this was "The inertia of the heavy block doesn't allow the egg to break" but I don't really get it. I mean, wouldn't the same force be 'transferred' through the block and act on the egg? The same way if I push one block that touches another, the both will move?
Ps: A similar experiment can be found here, if my explanation was not clear: