Tuesday, January 27, 2009

Homeschooling in the Bathroom

I'm doing a unit on construction with the kids in our co-op using a fabulous book called The Art of Construction: Projects and Principles for Beginning Engineers & Architects .

Last week we covered elasticity and plasticity.

A structure behaving elastically bounces back to its original position after being deflected. A structure behaving plastically develops a permanent deflection. In other words it stays bent after you stop pushing on it.

I showed the kids photos of the Bay Bridge at its 50th birthday when the weight of thousands of celebrants bent the bridge. I remember this scary event back when I was a senior in high school.

Here is the bridge demonstrating its usual elegant curve.

Below is a picture of the bridge during the festivities, when hundreds of thousands of people walked from either side of the bridge, met in the middle and had nowhere to go.

The weight of all the people caused a deflection--the bridge actually flattened out. Look on the underside of the span between the concrete and tall metal suspension columns. See how it lost its curve?

Fortunately the bridge behaved elastically and bounced back.

After looking at these photos we watched a video of the Tacoma Narrows Bridge which, after 70 minutes of behaving elastically, developed a permanent deflection.

This week our lessons have been brought home. The kids are watching as our bathroom is demolished. Dry rot had weakened the floor joists so we had to tear out the floor. While we were at it we decided to tear out the ceiling, too (to raise it and put in a skylight), and, what the heck, everything else.

The kids keep running to me with updates on the demolition.

I love it when life steps in to teach the kids and I can just sit back and blog.

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