Re: da/dt = jerk?

[William Beaty <billb@ESKIMO.COM>]

On Sat, 6 Nov 1999, Leigh Palmer wrote:

> Now it is true that there is a jerk involved here, but it has
> (ideally)infinite magnitude. The magnitude of the jolt felt is not
> related directly to to the magnitude of the jerk; "jolt", if I may
> coin a physical quantity, is the change in acceleration, delta a,
> and is unrelated to the rate of change so long as the time interval
> involved is sufficiently short.

Seems that "Jolt" as a term is already in use as a synonym for "Jerk"
(see below)



Interesting bit from the sci.phys FAQ:
http://math.ucr.edu/home/baez/physics/jerk.html


   Updated 18-January-1998 by PEG
   Original by Philip Gibbs 21-September-1996

          What is the term used for the third derivative of position?

   It is well known that the first derivative of position (symbol x) with
   respect to time is velocity (symbol v) and the second is acceleration
   (symbol a). It is a little less well known that the third derivative,
   i.e. the rate of change of acceleration, is technically known as jerk
   (symbol j). Jerk is a vector but may also be used loosely as a scalar
   quantity because there is not a separate term for the magnitude of
   jerk analogous to speed for magnitude of velocity.

   In the UK jolt has sometimes been used instead of jerk and may be
   equally acceptable.

   Many other terms have appeared in individual cases for the third
   derivative, including pulse, impulse, bounce, surge, shock and super
   acceleration. These are generally less appropriate than jerk and jolt,
   either because they are used in engineering to mean other things or
   because the common English use of the word does not fit the meaning so
   well. For example impulse is more commonly used in physics to mean a
   change of momentum imparted by a force of limited duration [Belanger
   1847] and surge is used by electricians to mean something like rate of
   change of current or voltage. The terms jerk and jolt are therefore
   preferred for rate of change of acceleration. Jerk appears to be the
   more common of the two.

   As its name suggests, jerk is important when evaluating the
   destructive effect of motion on a mechanism or the discomfort caused
   to passengers in a vehicle. The movement of delicate instruments needs
   to be kept within specified limits of jerk as well as acceleration to
   avoid damage. When designing a train the engineers will typically be
   required to keep the jerk less than 2 metres per second cubed for
   passenger comfort. In the aerospace industry they even have such a
   thing as a jerkmeter; an instrument for measuring jerk.

   In the case of the Hubble space telescope, the engineers are said to
   have even gone as far as specifying limits on the magnitude of the
   fourth derivative. There is no universally accepted name for the
   fourth derivative, i.e. the rate of change of jerk, The term jounce
   has been used but it has the drawback of using the same initial letter
   as jerk so it is not clear which symbol to use. Another less serious
   suggestion is snap (symbol s), crackle (symbol c) and pop (symbol p)
   for the 4th, 5th and 6th derivatives respectively. Dork has also been
   suggested for the sixth derivative. Although the reasons given were
   less than entirely sincere, dork does have an appealing ring to it.
   Higher derivatives do not yet have names because they do not come up
   very often.

   Since force (F = ma) is rate of change of momentum (p, symbol clashes
   with pop) it seems necessary to find terms for higher derivatives of
   force too. So far yank (symbol Y) has been suggested for rate of
   change of force, tug (symbol T) for rate of change of yank, snatch
   (symbol S) for rate of change of tug and shake (symbol Sh) for rate of
   change of snatch.

   Now class, repeat after me...
   "Momentum equals mass times velocity!
   Force equals mass times acceleration!
   Yank equals mass times jerk!
   Tug equals mass times snap!
   Snatch equals mass times crackle!
   Shake equals mass times pop!!

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