Force and motion
Force and Motion
Is there a Third Category?
Students may wonder about the pop-ups that produce up-and-down motion in the middle of a page, rather than along the gutter. These are compound pop-ups, which use a parallel-fold as the input to an angle-fold.
Later, we’ll see how to make them. Meanwhile, it might make sense to call them Type C, as in the diagram below.
A Type C Pop-up
The video below shows a Type C pop-up that has two outputs, each producing up-and-down motion on the side of a page, rather than along the gutter. We will learn how to make this type of pop-up in Lesson 11.