Interesting Concept and visual for Finding the Y-Intercept and thinking about parabolas

The question was asked, "Does anyone have an interesting activity that involves a quadratic intersecting a line?" And an idea began with this video, from PBS on String Product.  I had to share this resource because it is a cool concept to think about.

Some adults want to the know "why" math works like it does, so having videos or models help.  Think about a suspension bridge and all the math used to create these. Here is a short video about a Leonardo Da Vinci Bridge. The math (& physics) can be seen and this can create a great discussion in our classrooms about the "why".

Does anyone else have any interesting videos or resources to share?