Science Club - Tacoma Narrows Bridge

This weekend was our eighth session of Science Club! Topic:

The Book of Massively Epic Engineering Disasters:
33 Thrilling Experiments Based on History's Greatest Blunders
by Sean Connolly

I wrote a blog post previously with my planning notes when doing this block on Zoom. Now I get to do it IRL with a group of students!

For each disaster I'll share my up-to-date notes and some photos. On April 30 we learned about the Tacoma Narrows Bridge in Tacoma WA.

- recall last week's disaster (The Hindenburg)

- read "The Tacoma Narrows Bridge" information from The Book of Massively Epic Engineering Disasters, pp. 99-103

- do experiment #16 "Damping Tactics"

for each team (set up one):

a playground swing

two full gallon jugs of water

rope

stopwatch

Since I don't have a playground swing, I got permission from my neighbor to try this experiment using her hammock. So we packed our clipboard and pen (for making our data table), two full gallon jugs of water, two lengths of handmade rope (Zac made this at the Maple Syrup Festival and was very proud that it was being used for something so important), the book with the experiment protocol in it, and a stopwatch. We walked in pairs very carefully up the street a few hundred feet. It wasn't a long field trip but it felt special!

When we got to Miss Aleza's yard, we did the experiment as described in the protocol. It didn't actually work out. We are not sure if it was because a hammock is really not the same as a playground swing. You move gently for a long time in a hammock after you've been pushed. Was it the fact that it was a hammock that made the difference? Or was it that the wind was so strong that day that it kept blowing the hammock and making it move? It was interesting all the same. I recommended to the children who have swings at home that they try this experiment and let us know what happens.

Even an experiment that "doesn't work out" is an important learning experience. You still are practicing following an experiment protocol and keeping a data table. You are also getting some really authentic practice in critical thinking. What are some of the reasons why the experiment might have failed? What would you change about how you set it up, and why??

It's all about having a growth mindset!!! (If you missed it, check out my blog post on Growth Mindset Resources - Pop, Buzz, Zap!).

The conversation leading up to the damper experiment was super interesting as well. Before we walked down the street to Miss Aleza's, I asked the children to predict what would happen (would adding the water hanging down cause the swing to come to a stop more quickly or more slowly). One child said he thought it would speed the swing up (causing it to take more time before it came to a complete stop) because the swinging gallons would act like pumping your feet. I thought that was a really interesting idea!

One child began to say that it would speed the swing up because the extra weight would make it swing faster... but I stopped him mid-sentence. Remember the experiments with the pendulums (The Leaning Tower of Pisa - Mar 26)??? No matter how many washers we loaded onto those S-hooks, the period of the pendulum did not change.

Pendulum experiments are interesting because I've done them over many years with many different ages of children and I've NEVER YET seen transfer, ie. they cannot apply what they have learned about pendulums during the experiment (mass is not a factor) outside the scope of the experiment to a novel situation. Children still will make hypotheses in other experiments that you can see are based on the unchanged idea that heavy things fall faster.

I was actually really glad that this came up, however, because I hadn't made the connection between the swing experiment and a pendulum until we had that chat. A child swinging on a swing without pumping his/her legs is acting exactly like a pendulum. And so, really, a better connection might be to imagine what would happen if you put dampers on your pendulum!?!

What would happen if you attached two short lengths of string on either side of the S-hook with its washers, and tied nuts to those strings, so that they were swinging freely while the pendulum was going back and forth? Would the pendululum speed up or slow down? I do love S-hooks for pendulums because you can so easily load them up with more washers... and this would be really useful because you could slip the nuts onto the S-hook first, along with the washers, and then tie them to their strings so that they can swing. So the mass is unchanged and you are able to see the difference that the two strings and the extra swinging back and forth makes.

I would LOVE to try this. Dampers on a pendulum! Who would have thought?

Just add a few nuts to the pendulum kit!

- experiment with making a model of the Tacoma Narrows Bridge

This was my own idea. I always like us to have more than just one activity for a disaster. I just happen to have these really cool XL folding dining tables from ALPS Mountaineering that I bought last March when we were setting up the Outdoor Classroom. By the way, I love these tables and I highly recommend them!!!! The clay color is actually bronze with beautiful flecks in it that sparkle in the sunlight, and it's on sale right now for $89.10!

Because of the way the ALPS Mountaineering tabletop pieces are made in sections (thin slats held together by bungee cords threaded through them) and can roll up or open out flat when you disassemble/assemble the tables, I got to thinking. Could we use these flexible tabletop pieces to create flexible models of Galloping Gertie (the nickname of the bridge)?

Yes, folks, it's never a good sign when the workers building the bridge complain of seasickness. But it got worse when the bridge opened for traffic. We loved the section of the book on page 101 where Sean Connolly writes, "Once the bridge opened and its reputation for moving grew, thrill-seekers began to arrive. They were attracted by the fairground excitement of seeing oncoming cars disappear and then reappear as the deck moved up and down in the wind." YIKES!

for each team (set up two):

a collapsible tabletop, shown above

a wooden car

8 wooden peg dolls to act as onlookers

Their task was to try to set up a model where a peg doll onlooker standing and looking at the bridge would see the wooden car on it appear and disappear as the deck of the bridge rose and fell. (By the way, no one was hurt in this disaster. On Nov 7, 1940, someone from the Bridge Authority found it moving more than 3 feet up and down every two seconds. He halted all traffic. Within half an hour the bridge snapped in two and collapsed.)

I was glad I thought of this because they had a blast!

- pass out Science Club notebooks, have each child draw and write notes about his/her favorite experiment or about the disaster itself

While they were drawing in their notebooks, I grabbed Bridges and Tunnels: Investigate Feats of Engineering with 25 Projects by Donna Latham and looked up the Tacoma Narrows Bridge in the index. It was in there and so we read page 68. I also read them Twenty-One Elephants and Still Standing by April Jones Prince (this is about the Brooklyn Bridge, which opened in 1883).

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