Oct 28, 2009

Story: I'm a klutz

I'm a bit of a klutz. I don't think it's because I have an artificial leg. I just don't think my brain and my body are always in sync.

For example, one day, I decided to turn and walk into the hanging copper letter holder. I don't know why, but after walking smack into it, I realized, I had a scrape on my glasses. The next thought I had was, thank goodness I had glass glasses when I went through puberty. Since we got my glasses shipped from Hong Kong, I would have been twitching with a phantom scratch in my sight for months.

I usually use this story when we cover material properties, particularly hardness - the resistance to abrasion or indentation. My polycarbonate lenses are not as hard as my old glass lenses from my teenage years.

The concrete example helps students generalize their understanding - and I suppose knowing their professor is a klutz is endearing to them. Someone usually pipes up - what about breaking? If glass is hard, why does it break? Ah, good question. I ask for particulars on how it breaks... is it dropped or do you, for example, sit on it, and then it breaks?

This is a perfect segway into the terms, strength and toughness. It twists up the mind sometimes to think of these as different. If we can pile weight on top of my lens, for example, and it doesn't fail, then it is strong in compression. However, if it cannot absorb a high amount of energy put into it, for example, through a hammer blow or a drop on the floor, then it is not tough. Glass is strong and hard, but not tough.

As my sister, the English major, pointed out. Each word has its own definition. In engineering, terms are often different because they are defined, thus measured, differently. Concrete examples help tease out the differences and tie those definitions to past experiences. And apparently, my being a klutz helps students remember those past experiences better.