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: