# When the Teacher doesn’t know the answer… Buildings and More

As it happened, this week was an interesting one for me because I went into each iSchool class at Forestville with a question – and no correct answer.  In both classes, I relied on the interest, creativity, and imaginations of the students to drive the class.  And in both cases – it worked!  In this post I’ll discuss Thursday’s Innovation Lab. In the next post I’ll write about Science Magic.

In last week’s Innovation Lab I challenged students to build a tower using only index cards, scissors, and masking tape.  Students had only one absolute requirement: that the tower hold up 3 foam squares for 10 seconds.  Otherwise, students were free to use any design they wanted.  However, I did “charge” them for the use of index cards – \$1 a piece – and I stated that I wanted the tower to be TALL, STRONG, and CHEAP!  We talked a bit about how this challenge actually mimics real life situations that engineers face, when they must balance the competing objectives of maximizing strength and height while minimizing cost.

I came to class armed with information on physics and building shapes. We started class by discussing some of the forces that act on buildings, and we used erasers to model and feel those forces.  So we squeezed, stretched, bent, and twisted our erasers to learn about compression, tension, shear, bending, shear, and torsion. We reviewed an activity that we had done earlier in Innovation Lab showing that triangles are stronger than squares. We also learned about columns and tested the difference between round columns and square columns.  Students folded or rolled and taped sheets of 8×11 paper into columns, and then we tested them in a strength competition.  We stacked National Geographic magazines (which are thick and heavy) AND a laptop on top of similar arrangements of 8 columns of each shape.  The square columns fell over as we were piling magazines on top of the laptop. We may have had 15 or so magazines on the square columns. The round columns held our entire collection of magazines (25+) and the laptop.  After this exercise, older students discussed how corners in a square column direct weakness to concentrated points, versus round columns, which spread out weaknesses across their entire surface.  Follow this link to a helpful PBS webpage.

For a bit of fun we also tried to make columns out of index cards that would hold up a student, but we weren’t successful – yet!

Then, it was onto the challenge, with students working together or individually to build their towers.  It seemed that all students – younger and older – attacked the challenge with gusto, even if they were at times frustrated with the myriad options they could have – Triangles! Squares! Stacks! Folds! Which to choose?  This was an area in which I had to bite my tongue. The truth is that I don’t know what the “best” configuration is when building an index card tower. There are thousands of great designs and pictures online – but no single building shape or design that stands out.  So rather than push my opinion, I encouraged students to try out their ideas and reminded them of the properties we had already discussed. There were also challenges within teams – in fact, those students who worked as a team did not finished a tower before class.  We’ll work on teamwork some more!

Students were excited and proud of their buildings.  Most students finished a tower and all towers held up the three foam blocks.  Some towers were short but sturdy, others were tall but expensive, and one was tall and inexpensive, but swayed a bit. We measured the height of each tower and counted cards.  I asked the older students to do a cost-benefit (# cards/height) analysis to help figure out which tower I should “invest” in.  The design with the lowest cost-benefit ratio was the tall and inexpensive structure.  We then discussed whether I should invest in that design, considering how much it swayed. Could I trust it?

There are many many entries online about index card building challenges – they are all different.  Regardless of the lesson design, this challenge is a winner. It is engaging, empowering, and educational for students, and easy and inexpensive for teachers.  Win-win!  I am happy with this approach to class – this time.  There are times when the teacher really does need to know the answer, I think, so as to guide students to the facts that really are important in life.  And there are others – like this one – when it is the process of learning and imagining that matters most.

Testing a tower to see if it would hold up three foam blocks