Δt = 0.0333s; T = 30.0 Hz; 1px ≘ 0.126cm
Both the image of impact and the image after that edited together. I used the minimum distance, ie the last bit of blur of the 1st image and the first bit of blur of the 2nd. The ratio of the speed of the “blade” and the speed of the “stone” is 212/116, that's 1.83, which means the “stone” has almost twice the speed of the “blade”. Q.E.D.