Originally Posted by spacediver
I don't know enough about whip dynamics and whip waves to fully answer your question, but yes, that backwards motion before the snap does seem to increase power. Probably more relevant in the case where you are generating a true continuous wave. In the example I illustrated, if anything it is more of an approximation of a whip wave.
Nevertheless, wave or not, the figure still illustrates the conservation of angular momentum principle. You will get a successively faster joint motion as you move up the three links.
And yes, you would have to start rotating the black piece from a non-locked position (and in the figure it's already in locked position).
The whip is a very coarse analogy to serve mechanics, IMHO. A whip, because of its flexibility, is capable of sustaining a wave that operates on a continuously reducing amount of mass, and so when the initial momentum is transferred to the relatively small amount of mass near the tip, it will cause the tip to move very fast to maintain the initial momentum and thus cause the cracking effect as it breaks the sound barrier. The arm, however, has three joints where it is flexible - shoulder, elbow, and the wrist. There is no question of the upper arm or forearm being able to sustain a wave, because they are not that flexible! The whip analogy therefore cannot apply literally, I believe, and torque developed at the joints will be the dominant factor in creating racquet head speed. The whip is a great visualization, however. IMHO, of course!