Reflections on Ball Bounce Challenge

About a week ago, I posted a quick bit on the benefits I come across using Twitter to expand my profession learning community.  This particular post revolved around the idea of actually doing some physics the first couple days instead of doing the routine syllabus check and other typical 1st day "to-do" things.  While glossing over some potential activities, I had come across Frank Noschese's blog which included a fun ball bounce challenge activity with a high-speed camera.  After consulting with Frank via Twitter about the logistics of the activity, I decided to give it a try.

The first day went a little something like this:
In front of me are several balls.  As you can see, some are tennis balls and some are golf balls.  It shouldn't be much of a surprise that when I bring each ball up and drop it, the ball bounces back to a certain height.  Each ball bounces higher the higher I start it and, as you can see, the golf ball appears to have more "bounciness" to it.  We aren't going to concern ourselves with WHY this happens right now--that's for a later time.  However, we are going to use this phenomenon to collect some data and try to make some bold predictions.  
I have a very specific goal I want each group to try and achieve: start the ball at the appropriate height so that it bounces back up to a target height that I have already designated for you.  Keep in mind that you will not be given any practice rounds and you will not be told the height I want your ball to reach until we are ready for the challenge itself.  You and your group members must decide on how you are going to do this......SO GO!

At this point, groups got their balls (tennis or golf) as well as a meter stick (or 2) and I quickly began to see a variety of things happen.

• some groups simply dropped their ball against a meter stick and "eyeballed" its bounce height
• some groups dropped their ball and, using their iPhone, recorded its bounce height so they could view it later
• some groups only dropped the ball once and decided that one data point was good enough
• 1 or 2 groups really didn't know (or maybe care) what they were doing and just sort of bounced the ball a few times 

From my perspective, I thought all of this was interesting for a couple reasons:

1. It gave me insight toward how students value data.  Is one data point good enough or should I have more?  How accurate do I need to be and are there measuring tools or techniques that will allow me to attain more accurate data?
2. It also gave me insight as to who already sort of "gets it."  One quarter of my class qualifies for special education and I have several others who have demonstrated poor academic skills in the past (based on either already having them or simply hearing it from other teachers).  This is not to say that "teaching this class physics will be impossible" but it does have a profound effect on the extent to which I can assume certain skills my students have as a teacher.

We spent the entire first period, which just so happened to be a short day due to an earlier school assembly, collecting our data.  I assigned a number to each ball so that they would have the same ball the following day when attempting the challenge.

The second day:

I told the students I wanted them to have their ball bounce to a height of approximately 62 cm.  This was essentially the height of two lab stools.  As I walked around the classroom trying to get some insight as to how they were going to determine their starting height, I noticed the following methodologies from the students' perspective:

1. "Based on our data, the ball seems to bounce to a height that is about 85% of its original height.  Therefore, we're just going to calculate the original height so that 85% of it is 62cm."
2. "We found that our ball loses (some amount) of inches in height for every 1 foot we bring it down"
3. "We know that the ball has to start somewhere above 62 cm so we are just going to sort of eyeball it and hope that we come close"
4. "Our data shows that for every 10 cm we raise the ball, it bounces about 7 cm.  So we will try to use that so it bounces to 62 cm"

Again, I didn't really care how the students went about collecting their data and how they were going to use that to make the ball bounce to the target height.  The physics behind this activity is actually pretty cool and fun but it has its own place in the course down the road.  What was cool to me was that when given the freedom to develop their own experimental procedure, students sometimes come up with cool and creative ways to achieve the objective.  Sometimes ways that I would have never thought of before!  This can also go the other way too.  If given the freedom to choose, some students will essentially do nothing and any nudge I try to give them in the right direction will sort of just go right through one ear and out the other.  But that's a different story.

So what did the results of the challenge look like?

• As you will see in the videos, I placed a meter stick between the two stools.  I tilted it upright so that the broad side was facing the camera.  I told the students that if they got any part of their ball level with the meter stick, they succeeded in the challenge.  Because this was for fun, I thought it might allow some room for error.  Winners got to reach into a bag of mini Twix and take a handful.  I ended up going through 3 bags!!  All very large hands from teenage boys....

Winner

Winner

Winner

As you can see from the videos, some are pretty good and some went just went horribly wrong.  However, those that either won or got really close all had one thing in common: they had a plan that allowed them to collect enough data and come up with some sort of way to use that data to make a prediction.  It was their first attempt at using models to make predictions!

Overall, the activity was fun.  The students had a good time watching the youtube videos as a class and seeing who actually won.  It was easy for me to record the videos and quickly upload them to my youtube channel that same class period.  I will add a few new things to the activity next year so that each group provides some sort of data and each group makes a whiteboard that shows their methods as well as data.  This activity was really cool and I'm sure the students appreciated not having to spend yet another class period listening to their teacher read the syllabus :)