Barbie Bungee Revisited and Better Than Yours Class Lists

This year I've taken away a lot of my step-by-step instructions for the Barbie Bungee activity that I'd posted 1.5 years ago. They get no handouts, only some verbal instructions:

[Pointing to the ceiling] See that gob of tape up there? That's leftover tape from previous years where Barbie had taken her jump. It should be at 3 meters up. Well, a small ruler will come out perpendicular (somehow) to that pole where the tape is, and that's Barbie's jumping platform. The ruler is like her diving board.

The goal is to give her the most thrilling jump — her head dips as close to the ground as possible without actually touching it. Yes, her hair hitting the ground is fine. Her jump line is made of rubber bands tied together with slip knots. (Why must we use brand new rubber bands?) You'll work in groups of three, says Instant Classroom.

So, aside from the Barbie doll, what do you think your supplies will be?
Rubber bands! How many? Lots! A hundred!
Try six. Actually seven, but one must be completely wrapped around her ankle, like this.

With only 6 rubber bands, your job is to figure out how many more rubber bands she'll need for the most thrilling jump from 3 meters.
Can we weigh her?
This is like the Vroom car!
So we have to graph, then do the extension thingy. Extrapolate. Oh, the equation is in slope-intercept form!

(We've been looking at word problems and writing linear equations that would be more appropriate in standard form or in slope-intercept form.)

Your team will have until the end of tomorrow's class time to submit your number of additional rubber bands you'd want.

For easier management of the rubber bands, I get them ready in bundles of 7, one to each group for testing and data gathering, and in bundles of 10 and extras to give out as requested on jump day.

I liked the messiness of their initial work. (I didn't give a handout or many instructions for Vroom! either, and they did fine.) Kids doing whatever they think they should do, measuring incorrectly, plotting ill-looking graphs, talking and criticizing one another. I was debating when I should intervene, but it was good for me to just observe and listen in.I waited until the next day to point out stuff. Actually I never told them what they should do, I tried instead to ask them how something should be done. I don't think one single idea came from me — someone always had the answer I was hoping for, so all the "correct" ways to do things came from them. My phone apparently didn't have enough memory after this one clip. It was fun. (One kid also brought up that this was like the Stacking Cups lesson that we did.)

This might seem to you a DUH! share, but I only thought of it earlier this year, and I feel like I invented the paper clip. We all have class lists, of course. But is each of your class lists on a strip of paper like this? And in different colors? I didn't think so.

I have semi-thick stacks of these to use for just about everything. What a pain to write down kids' names for this and that. Instead I just pull out a strip and highlight so-and-so's name and note the reason.

I staple one set of strips together, put a date on it, and kids pass it around to each other to sign in for after-school help — they just need to put their initials next to their names.
Those who need to come in at lunch recess get their names highlighted on the strip.
I use it as a hall pass when I need to send 2 to 3 students at a time to the library.
I highlight a kid's name whose parent I need to contact, then use the back of the strip to make notes from our conversation.
It's a great tally sheet for whatever during class.
Endless uses.

10/11/13 10/11/13

Vroom Vroom

I normally share a lesson that I've already done with students, but I'm still tweaking this one and needing to write some thoughts down before my noggin turns back into soft tofu. I bought these 14 pull-back friction toy cars (2 sets) for $30 at Costco. Amazon posts a video of how well these soft squeezable cars can stand up to toddler abuse.

On your mark...

Each team of 3 students gets 1 car.
How far the car moves forward depends on how far it gets pulled back — good lesson too for talking about potential and kinetic energy.
The challenge is to get your team's car to go a certain distance (reach finish line) without going over. This distance is not revealed until later.
To predict for how much pull-back a car needs to go a certain distance, students "test drive" their cars for pull-backs of 2, 4, 6, and 8 inches.

Get set...

Students are instructed to take measurements from the car's front wheels.
The blue tape marks the starting line. Front wheels line up at the front of the tape.

The car is then pulled back a certain distance — here it's 2 inches — and let go.

When the car stops, the distance traveled is measured from front of wheels to front of blue tape. Looks about 13.2 inches here.

Go!

Teams do 3 trial runs.
Record and graph data on Desmos.

Now teacher reveals and marks the distance each car needs to travel without going over. Say 15 inches.
From graph, students extrapolate what the pull-back distance would need to be for car to move forward 15 inches. This distance is recorded and cannot be changed.
Teams line up with their cars — one at a time — to pull back and let go!
Winning car is one that reaches closest to finish line without front wheels going past it.

Considerations

The cars roll best on bare floors. My classroom is carpeted, so we'll need to do this outside.
It's fun that the cars actually vary in speed for same pull-back distance. The sports car (bottom left in above picture) is fastest.
My kitchen floor is not big enough to test longer than 8-inch pull-backs, but the graph appears more parabolic.
The data looks pretty awful, doesn't it? Kinda? Maybe?

Ginny from Mathalicious was in the kitchen when I was playing with these toy cars. She shook her head and wondered if empty nest syndrome got the best of me. No matter. I think this will be a lot of fun. Will report back and post some pics.

[Updated 12/01/13] Jon Orr did this lesson with his Grade 9 students and wrote a great summary on his blog.

Here are a few pics from my class:

And a couple of video clips: