I don’t believe it is the case any longer that public schools offer vocational classes. I remember in middle school (junior high) I took a wood shop class. I enjoyed that experience a great deal. They offered metal shop and automotive shop classes as well.

I imagine the following film might have been shown in an automotive class. It’s wonderful how it describes the problem and then the solution that differential gearing provides in a way most students can probably understand.

An educational look at how things work. More films like this, please.
(The actual education content begins about 1:55 into the film.)