Thanks for posting this. Neat experiment! Part of the result depends on how close the camera is to the action, though. The nail is moving 3.5mph, but it is only 15 feet away from the camera. If it were further away, it would pass through a smaller amount of the frame, so there would be less apparent motion to the camera from that motion of 3.5mph, so less blur. Of course, basketball players are moving much faster than 3.5mph, so your point is well-taken.