# How Long is the Roll?

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My conceptual physics class was chugging along just fine the other day. Then a kid asked for some paper towel. When I took out a giant roll from under the sink, the day’s lesson took a detour which would make Dan Meyer proud.

Kid: “Whoa! How long would it be if you unrolled the whole thing?”

Me: “I don’t know…you want to find out?”

Kid: “Yeah!”

Me: “OK. But you’ll need to make a prediction first.”

How long is the giant roll?

Takin' data with a smaller roll

Class data. Groups measured different amounts of paper towel. Who will be closest to the actual roll length?

Time to unroll!

Final analysis with an attempted shot at evidence-based reasoning.

### 5 responses to “How Long is the Roll?”

1. Very cool! How long did this take?

• It took 2 days. The first day was setting up the problem in their notebooks, having students write up a brief proposal as to what data they wanted to collect and why, taking data, and collecting predictions from all the groups. Some groups massed the same length (though not the same piece of towel) several times, some groups massed several different lengths, while others just massed one length of paper towel.
The second day involved 15 minutes walking to the football field and back, 10 minutes to unroll and clean up, and the remaining 15 minutes to compute percent errors and explain what relationship (if any) existed between how far off predictions were and how much paper towel was massed.
It wasn’t the most challenging activity, but I wanted to build a class culture where students’ questions are valued and explored. If this had been my calc-based physics class, we would have predicted the length using calculus as well.

2. I am proud. Nice work.

3. Fantastic!