Students begin addressing some of the issues that arose in Lesson 2 by investigating the shape of a pop-up before and after the book is closed for the first time. They discover that a pop-up mechanism forces a fold to be made at a specific location in the pop-up piece.
For each student:
Using the template: Provide each student with materials and demonstrate how to assemble the template.
The edge view before & after: Then ask students to predict what it will look like from an edge view after they fold it. See a video and diagram showing what happens.
Outcome: The book will shape a fold in the pop-up. From an edge view, the strip will look like an arch before the book is closed, and like a triangle after the book is closed and then opened completely.
Where will it fold? In the next experiment, students add another strip to the book, in a different position. Then they close the book and explore whether the second strip will fold in the same place.
Outcome: The location of the fold depends on the page positions.
Will it respect my fold? Finally, they begin with a folded strip and run an experiment to see whether the book will respect their fold.
Outcome: The book will shape a second fold, usually in a different place from the first.