In Episode 6 I mentioned a thought experiment with a concrete-filled rugby ball. I have used this model for years and knew it came from a text book long ago and I have since been searching for it. I was convinced it came from Peter Warren, the head of department where I did my teacher training and author of one of the books that was used to teach me back in the early 80s. It turns out that Pete is still teaching, but did not draw the cartoon.
It actually came from Physics for You by Keith Johnson, and it is still available, new from Amazon in the 5th addition. I actually own a Johnson (it has sat on a shelf in my office untouched for years) and did not think to look in it until I had sourced a couple of Warrens from amazon. The character kicking the rock (in this case) is Professor Messer. I assume Johnson drew them all himself, as did Pete in all the cartoons in his books. I excitedly looked up @ProfessorMesser on twitter to see if he had an online presence but it turns out to be a real person.
One of the Warren books I sourced is a gold mine. It is the advanced physics laboratory book and this would be a super resource for anyone new to A level teaching. I got it for 20p just a week ago but a quick check on amazon shows it is now £28+! It contains many practicals that I consider routine but has given me some new ideas too. For example, my school does not have a position sensor/force sensor etc. so I have not been able to datalog damping. This book has a beautifully simple way of doing it: attach a magnet to a hanger boinging on a spring, bounce it up and down inside a coil and measure the current in the coil.