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Monday, January 3, 2011

Why today I was an amazing teacher.

Picture this.

It is the first day back after a long holiday break. The students are not happy to be back at all. The teachers are not much more so. I am already hopelessly behind where I need to be right now. I need to find something to attract their attention and refocus them on what we learned.

Time for the slinky demo.

Standing on a tall table I held the uncoiled slinky from the ceiling. It was hanging stationary (relatively speaking) and then the magic happened. Before I said anything; not even one question was asked. A student made a comment that the slinky coils were further apart at the top than at the bottom. I said nothing. Another student made a comment that the forces must be different throughout the slinky. I said nothing. This led to a 10 minute debate about the properties of a slinky and where forces would be greater. Students got up and drew pictures on the board. They broke out into little groups truly working through the problems. I said nothing. Finally one of my students said "Wait a minute. Mr. B hasn't even asked us a question." As they all turned to me I had the largest grin I think I've ever worn in the classroom. I was so proud and excited for them. They were engaged. All of them. Without asking a question. Without prompting anything more than holding up a slinky.

I told them "You guys are amazing. That was a brilliant discussion. I have never been prouder of you!"

I then went on to wow them with the slinky discrepant event. They made force diagrams for everything. It was like we had not taken a single day off.

If I wasn't convinced that modeling works at this point there would be no way to deny it after today. It is amazing what students can accomplish when we teachers get out of their way.


  1. This is really fantastic, and a great way to get kids away from massless ideal springs.

    One of the most intriguing demos I ever saw about a slinky was very similar to this, but the professor asked the question, what will happen when I let it go. He then prompted the audience that he could think of three possibilities: 1) the bottom of the slinky will start to fall the moment you release the top, and it will fall as a big uncoiled slinky. 2) the top will fall first, and the slinky will contract, with the bottom not falling until the top reaches it or 3) some other completely crazy explanation.

    I remember seeing this demo when I was a new teacher and honestly not knowing the correct answer. This is one of my absolute favorites. I also think it would easily lend itself to video analysis. Could you film the fall, and see that the coil you release in your hand is falling with an acceleration greater than g?

  2. Hey John,

    That is actually the demo I did. I asked the question afterwards. But the kids were on such a roll I just let them run with it. They were doing everything I hoped they would do all year!

    The most amazing thing to me is the kids had none of the post holiday drop-off that you normally expect. I may have to borrow my friend's high speed camera to film it. I'll let you know if that happens.