Archimedes, centre of gravity and physics

Dr. Julius Sumner Miller explains how to determine the centre of gravity of an object. 

This is, of course, a subject of interest in Judo.

It's applies even when the centre of gravity
isn't on the body of the object in question.



In my world, Judoka would have an option to pass a Physics exam by analyzing Judo
waza for examples.

this guy was a favorite of my high school physics professor. I've already seen all his videos.

when we were learning about COG analysis in physics 1, the textbook used a judo throw as an example problem. it turns out my professor used to do judo as a kid.

The classic explaining this in judo is:
Watanabe, Jiichi, and Lindy Avakian. The Secrets of Judo Tokyo: Tuttle, 1960.

Shindai Warrior wrote:Dr. Julius Sumner Miller explains how to determine the centre of gravity of an object. 

This is, of course, a subject of interest in Judo.

It's applies even when the centre of gravity
isn't on the body of the object in question.

https://www.youtube.com/watch?v=vYbBakL9Cj8

In my world, Judoka would have an option to pass a Physics exam by analyzing Judo
waza for examples.

Very inspiring teacher.

But down to business. If your judoka take the option to pass a physics exam by analyzing judo waza and are successful in doing so, then they are little geniuses, since the relevance for judo of what is shown in that video is quite limited. Kanô unfortunately made the same mistake. What is shown in the video differs in critical ways from what goes on in judo. Contrary to the objects used in the video, a judoka is not a rigid object. Secondly, a judoka is segmental, continuously moving. Thirdly, a judoka is composed of materials of different densities inside those materials there are shifting body fluids and inspired air and those shifts changing depending on the intensity, and to make that all a little bit more challenging, when judo is effected, it is actually not one but a composed couple of two judoka that make up that 'single' object. Determining the center of mass of that composed judo couple, yes, the student who is able to do that deserves more than just a pass in his/her physics exam.

The practical consequence of this is something most judo teachers have already realized: judo is a complicated technical affair and very challenging to transfer skills to someone else.

NBK wrote:The classic explaining this in judo is:
Watanabe, Jiichi, and Lindy Avakian. The Secrets of Judo Tokyo: Tuttle, 1960.

as a physics nerd, this is without a doubt my absolute favorite judo book of all time. it was the first one that really spoke to me, especially the back section with a vector-based breakdown of many techniques. I used this book to correct a lot of mistakes in my application of techniques. it is currently on loan to another nerd in the class, whom I thought would enjoy it as much as I did.