Tag Archives: energy

Video Analysis of a Bouncing Ball


Nothing earth-shattering here. I just wanted to share the activity we worked on today, which was an introduction to quantitative energy conservation by doing a video analysis of a bouncing ball. (Up until now, we were only doing qualitative energy pie charts.) Here are the handouts and the video:

The graphs from the analysis are just beautiful:

HeightTime VelocityTIme EnergyTime

Lots to talk about in those graphs!

Feel free to edit and reuse the handouts as you see fit. They’re not perfect, but I figure it’s better to share them than having them collect dust on my flash drive.

PS: I’ll sheepishly admit that I don’t do the whole suite of paradigm labs in the Modeling unit to mathematically derive the energy equations from experiments. But we do some simple qualitative demos/experiments to discover what variables would be in those energy equations. We start by talking about how the further a rubber band is stretched, the more energy it stores. Then we launch carts into a rubber band “bumper” (i.e., big rubber bands from Staples and two C-clamps) to qualitatively see the energy stored.

In doing so, we see that the cart’s kinetic energy depends on its speed and its mass. (Or is it weight? What would happen if we repeated the experiment on the moon?)

For gravitational energy, we can repeat the experiment, but have carts rolling down an incline. Or use the rubber band to launch the cart up the incline. I’ve also dropped balls into sand and looked at the depth to which they get buried. Either way, we see that gravitational energy depends on height and weight. (Or is it simply mass? What would happen on the moon?)

For elastic energy, we already know it depends on the distance the rubber band is stretched. Then, we can swap out the rubber band in the bumper with a stiffer/looser one to see the effects of the spring constant on energy stored.

Then, after we predict what the energy equations might look like, I just give them the actual energy equations, or have them look them up. (Gasp! See Schwartz’s A Time for Telling, aka Preparation for Future Learning.)

So, modelers, what am I missing by not doing the full-blown energy paradigm labs? How do you introduce the quantitative energy equations?

Red, Blue, and Yellow Angry Birds

Download the original video files:

Angry Birds for Google Chrome

You can now play Angry Birds in Google Chrome! This makes getting footage for video analysis much easier. Here you go:

Download the video file for your own analysis. I used Camtasia Studio (free trial) to do the screen recording.


#anyqs: Energy

Inspired by Dan Meyer’s blog post on his new Twitter meme, #anyqs, I started our unit on energy with this demonstration:

I asked students to write down any questions that came to mind. Here’s what they said:

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I would have had the students investigate their own questions and then share with the class, but I only have 2 slingshots. So we did it as a whole class demonstration. I also tweeted out the demo using the #anyqs hashtag. Your responses were similar to my students. Here they are, with the new demo modifications and outcomes:

The adding/removing of books was most perplexing to students and it was a great lead-in to the concept of energy conservation. The rest of the lesson was pure pseudoteaching, as I started throwing terms at them like kinetic energy, gravitational potential energy, and elastic potential energy. (No formulas yet, though.) I’m really bad at running effective whole-class discussions, so if anyone has any tips, fill me in!

What would you have done differently?