When you inspect the bar charts, it is evident that as the bob moves from A to D, the kinetic energy is increasing and the potential energy is decreasing. However, the total amount of these two forms of energy is remaining constant. Whatever potential energy is lost in going from position A to position D appears as kinetic energy. There is a transformation of potential energy into kinetic energy as the bob moves from position A to position D. Yet the total mechanical energy remains constant. We would say that mechanical energy is conserved. As the bob moves past position D towards position G, the opposite is observed. Kinetic energy decreases as the bob moves rightward and (more importantly) upward toward position G. There is an increase in potential energy to accompany this decrease in kinetic energy. Energy is being transformed from kinetic form into potential form. Yet, as illustrated by the TME bar, the total amount of mechanical energy is conserved. This very principle of energy conservation was explained in the Energy chapter of The Physics Classroom Tutorial.
I went on to work at Apple Computer on new multimedia and user interface concepts involving digital agents, animated user interfaces, speech recognition and distributed information access. In 1991, there was a sudden flurry of activity when Apple and IBM were trying to set up a strategic partnership. I became involved in the super-secret negotiations, and made the suggestion that what the world needed was a standard for multimedia that multimedia content creators could rely on to publish to (ultimately this is what HTML became). Based on these suggestions, Kaleida Labs was founded. Our work there developed a product called ScriptX , which turned out to be very similar to Sun's Java which was being developed at the same time. ScriptX had goals of supporting all forms of multimedia: text, images, audio, video, animation; being cross-platform (Mac and Windows), interpreted, object oriented, with a garbage collector to manage memory.