# Talk:Whipcracking

## whipcracking tricks

last month I've stumbled upon a TV programme about some cowboy festival in America. A lady did amazing tricks with the whip including hitting a penny off the tongue of her partner. `'Míkka 18:41, 30 July 2007 (UTC)

## Physics

The physics section mentions a vacuum, which is incorrect. The crack comes from the shock wave produced when the whip exceeds the speed of sound, and this does not create a vacuum. I checked the reference for it and it doesn't mention anything about a vacuum either. (Jatoo (talk) 12:55, 8 January 2008 (UTC))

in the explanation, the part where is says "the top of a car's wheel moves twice as fast as the car itself" seems not only counter-intuitive but also wrong. It is true that it's in the source but i can only suppose that is wrong. If no one responds to this in a week i'll change the article. C. M. - Engineering Student —Preceding unsigned comment added by 67.55.17.131 (talk) 02:08, 28 July 2009 (UTC)

don't. - Altenmann >t 03:48, 28 July 2009 (UTC)
I know this is an old post. But I assure you it is correct, however counter-intuitive it may or may not be. It can be demonstrated from the kinematics. Mostly for anyone else who doubts it: Imagine a moving car. The top of the wheel is moving forward with respect to the car at the speed of the car and the bottom is moving backward at the same rate. From a person standing on the ground though, the top is moving twice as fast and the bottom is completely stationary(if not it means the wheel is slipping).--75.80.43.80 (talk) 12:01, 15 April 2011 (UTC)

I agree with user Jatoo. A whip is not a car wheel. A loop in a whip is =not= analogous to a tire on a car. It is neither rigid nor fixed to an axle that imparts linear motion. There are at least three possible modes of motion in a whip that will cause it to crack. At least two of them do not involve forming a loop in the whip. See: http://home.comcast.net/~a-mcnibble/Rants/WhyWhipsCrack.pdf for information about modes of whip motion. This entry needs editing and I will undertake that in a few days. — Preceding unsigned comment added by 67.171.35.218 (talk) 18:26, 22 September 2011 (UTC)

Correction: I agree with user C.M., not user Jatoo in my above statement. In addition I will point out two more significant differences between a whip and a wheel: Whips easily exceed the speed of sound and the end of the whip can move more than an order of magnitude faster than the handle. Wheels seldom exceed the speed of sound and the maximum linear speed of the circumference of a vehicle wheel is always exactly twice the speed of the vehicle. These differences alone should make a thoughtful person suspect there is something basically different about the nature of the phenomena. — Preceding unsigned comment added by 67.171.35.218 (talk) 22:36, 22 September 2011 (UTC)

## Outdated

The thing about the 3rd British Whipcracking thing is outdated, somebody fix it. — Preceding unsigned comment added by 211.30.187.18 (talk) 00:30, 27 March 2008

## 200 decibels?

This is beyond extremely loud, and would make a cannon sound like dead silence by comparison; See This article and section. I don't suppose anyone has a more plausible number and a source for it? TJSwoboda (talk) 19:04, 4 June 2009 (UTC)

I went ahead and changed it. Even though the cited Discover article gives the 200 decibel figure, I cannot fathom this being right. If an expert can prove me wrong though, please do so. :) TJSwoboda (talk) 19:15, 22 June 2009 (UTC)

## Physics - Dubiosity on what is conserved

At present the article mentions conservation of momentum as the reason for the tip acceleration, however it is actually conservation of energy at play. The distinction is perhaps subtle (both would lead to tip acceleration) but they are different things and would lead to different quantitative result. Source-wise, this PDF (mentioned in an earlier talk topic) explains the crack in terms of energy conservation. Also there is this paper on a related effect for partially falling chains, also explained in terms of energy conservation. (That article is what brings me here. See also related discussion at Talk:Self-siphoning_beads.)

Physics wise I can offer two easy insights. First, there are forces applied between the stationary whip body and the tip, and there is tension all along the body of the whip. These forces transfer momentum between the tip and the person doing the whipping. The forces are oriented such that they decrease the momentum of the tip. Second, if tip momentum p were conserved then the energy (p2/2m) would increase as the tip mass m decreases -- where does this energy come from? In fact it is energy p2/2m that is conserved; momentum decreases as 1/sqrt(m), yet speed increases as sqrt(m). Hence, the crack. --Nanite (talk) 13:43, 25 October 2014 (UTC)

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