Here is the latest of my YouTube videos. It is an instructional video about swing arms and robot arm principles. The illustrations and animations utilize the VEX IQ build system, however, the principles can be applied to any robotic build system. I hope it will help you explain some of these concepts to your students! Robot arms-swing arms - YouTube
The Google presentation used for the storyboard of this video can be found at: Robot Arms -Swing arms - Google Slides
Remember you can customize this for your own by going to: File> Make a copy