Angular momentum

Apologies for being so quiet lately. I thought that I’d share this little blog post examining sayabiki (the pulling back of the scabbard with the left hand to draw the Japanese katana with the right hand) from the physicist’s perspective of conservation of angular momentum:

Sayabiki and Angular Momentum

This is an interesting point, although I think that it is more relevant to, say, the dynamics of a throw in Aikidō than drawing the sword in Iaidō. While I don’t doubt that using sayabiki to exploit the conservation of angular momentum does allow a more powerful draw, I think that the primary reason for sayabiki is simple mechanics: if one does not retract the scabbard, then the sword will not come cleanly out of the scabbard mouth — if the sword comes out at all, then its cutting tip will damage the scabbard and indeed the Iaidōka’s hand!


A Good Start

There’s something very nice about getting up early in the morning, before dawn, and spending a couple of hours in silent practice of Zazen and Iaidō, as I did today. The combined effect left me feeling very good for the rest of the day: settled, but not sleepy; exercised, but not over-exerted; energised, but not jumpy. Truly, a nice way to start the day.