Bull whips are seen as more of an American whip than any other. They were developed to help herd cattle and over the years have evolved a reputation as a brutal whip. Bull whips are no more brutal than any other whip. It all depends on the user.
Bull whips have a rigid handle with a wooden or steel core, and have a fall to which the cracker is attached. Bull whips usually have a second knot on the handle at the point where the handle ends. This is called the transition knot. American bull whips have a handle of 8-10 inches whereas Australian style bull whips tend to have longer handles of up to 18 inches.
This is largely dependent on the length of the whip and the preferences of the one throwing it. A bull whip is measured from the end of the handle to the knot where the fall is attached. The fall is not counted in the length.