# What's a change in jerk called?

I’m not sure how to make myself clear here, but I’ll try:

A change in position is velocity.
A change in velocity is acceleration.
A change in acceleration is jerk.
What do you call a change in jerk?

An election.

Actuall: jounce or snap, per wikipedia. But I don’t think it’s as accepted as jerk. Also per wikipedia the higher orders above jounce or snap are crackle and pop, which are obviously even less accepted than jounce.

4th derivative.

Bravo! Bravo, Bravo!

Bravo!

I read that as “An erection” and thought, yeah, that’s about right.

Incidentally, there are some deep reasons for why we only generally care about stuff up to acceleration. If higher derivative motions terms are relevant in the equations of motion for something, then the things Hamiltonian can reach arbitrary energies, which will cause it to spontaneously produce huge amounts of particles and quickly become catastrophic. See here: http://physics.stackexchange.com/questions/4102/why-are-only-derivatives-to-the-first-order-relevant

I was gonna say, “An inauguration,” but yours works, too.

Thanks very much Ludovic!

Coke out of both nostrils!

Supposedly, the Hubble Space Telescope engineers put limits on m/s^4.

I’ve never seen an explanation why, but my personal theory is this: when considering the linear aspects of angular motion, you tend to get one more derivative. A constant angular velocity means that points on the edge experience a linear acceleration. An accelerating angular velocity means points on the edge experience jerk. Hubble rotates around to aim, so obviously they care about this kind of thing.

So if the Hubble engineers clamp angular jerk–and this is a good idea, since too much jerk can cause undue stresses on a structure–then this is equivalent to saying there is a clamp on jounce/snap/etc.

At least that’s my personal explanation. But I’m no physicist.

SUPER-bravo!

Leave it to the engineers to ruin good physics. Bah.

Rollercoaster designers also pay attention to the 3rd and 4th time derivative of position. Apparently it’s these higher order derivatives that give a rollercaster that ‘out of control’ feeling.

Well done, sir. Well done, indeed.

Back in school, we were told the 4th, 5th, and 6th derivatives were “snap, crackle, and pop”.

This sounds fascinating, but I don’t follow it, and I can’t follow the explanation in the link. “…then the things Hamiltonian can reach arbitrary energies…” doesn’t read well to me (but of course I am missing something).

Any chance of a dumbed down explanation?

Dammit, I just thought of that joke while looking at the index, and opened this thread just to make it. Way too late, I see – it was the very first response. Kudos!

somehow “Term Limits” has to be an application.

Aww, I was 90 minutes late. That was exactly my reaction to the OP. Kudos.

I think **Ludovic **deserves some sort of SDMB award or something - that was a right fine response, sir.