Work done by friction is never conserved, since it’s turned into heat or sound, and we can’t get that back. It’s a non-conservative force. Other forces like gravity and speed are said to be conservative, since we can transfer that energy to a different form for a useful purpose. When you pull back a swing and then let go, you’re using the energy created by the gravitational force on the swing and transforming it into the forward motion of the swing as it moves through its arc. Energy from friction forces cannot be recovered, so we say that it’s an external energy, or work done by an external force.
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I know it can be hard when you have to stop and start the teacher. (Imagine if I were live in a classroom, and you just have to figure it out as we go, no “pause” button at all!) Did you download the workbook for each section? There’s room with each page (each page goes to a particular lesson) for your notes, and there’s also a brief intro near the top. Sometimes I need to stop and start something, watching it over and over until it makes sense, so I totally understand, it happens to me as well! I would just take it slow, and know things will get easier once you get some momentum with the program. And yes, initially it’s going to be slow, because you’re learning a lot of new things all at once (how to use the program, learning in this format, the concepts themselves, etc.)
I have a question about getting the most out of each video. I can’t seem to write that fast, so I constantly have to pause the video to get everything written down, but it’s hard to focus on the subject at hand. Do you think that doing the problem with the video and then rewatching the video itself would be a better idea to grasp the subject?