Capturing motion using the flash

1/6, f8, ISO 400

Homework for the last photography class yesterday was taking a creative photo with the flash using a long shutter speed. Up till now I was not very fond of using the flash, especially the built-in ones, but I am quite excited about it now. The possibilities are numerous and the results are very pleasing to my eye. Again, this has nothing to do with contemplative photography, but it is a very agreeable extension of my photography skills.

1/6, f10, ISO100

All these photos were taken in the Tv mode of my camera, so that I could control the shutter speed easily. The top photo is my house mate Laura whom I asked to shake her head so that her hair would flow about her. By using a slow shutter speed I can depict the motion of her hair and face and the flash freezes a moment of the motion.
The second image shows a colleague of mine who actually is a fervent kick boxer in his free time. I asked him to perform some classic moves with an imaginary adversary. The stripes on the wall behind him were formed by sunlight that shone through the blinds.

1/10, f8, ISO 100

The image above is a bit more subtle: this is my colleague secretary Mirjam typing away an imaginary email message. Here you can see the movement of her fingers and the motion instability of the camera on the keyboard.
So what do you think? Do you see possibilities using this technique?