RMT Basics, page 7

You Can Concentrate Tension

But, first, let's ask the question: "Why do most things break first in tension?"

The answer is: Because tension concentrates; and, where bending is involved, the concentration of tension can be intensified by leverage.

To see this, consider what happened when you broke the pencil:

Using the mechanical advantage of leverage, you concentrated your force on a tiny fraction of the material of the pencil.

This allowed you to stretch that tiny fraction and initiate a tiny tear that grew to a fracture which ultimately proved fatal.

Engineer Cruching Pencil from eraser

end

If you had attempted to crush the pencil, (either in a vertical or horizontal position), you would not have had the advantage of leverage to concentrate your force on such a tiny fraction.

You would have spread the force over a larger fraction of the material, and so you would have encountered much more material resistance.


You would have found the pencil		much more difficult to break.