rolling

This is actually been sitting around for a while waiting for me to post it. Here is another short Christmas-toy demo. I am going to pull this yo-yo at different angles and on two different surfaces. Check it out. What is going on here? Let me look at the first case where I pull the yo-yo and it slides without rolling. Here is a diagram. Normally, I would just say - "hey - a free body diagram". And this is one, but you have to be careful. Normally, a free body diagram treats an object as though it were a point mass. You can't do that in this case because you have to consider rotation…