Thing that I learned yesterday (one among many, but this is the most memorable):

Jan 26, 2014 12:17

The first derivative of distance related to time (change in distance over time) (dx/dt) is velocity ( Read more... )

Leave a comment

kengr January 26 2014, 19:41:56 UTC
I have trouble seeing situations where those would be relevant (or measurable).

Well, not jerk, but...

Don't sup[pose you have the formulas for distance versus time for each of them. I have the one for jerk somewhere. Without checking my notes, I think it's

d = 1/6 * jerk * t^3

Reply

janetmiles January 26 2014, 21:53:12 UTC
I don't know if there are practical applications, either, but it pleases me that the names exist. Oh, wait, I think he said jounce is used in rocketry, something to do with directional boosts.

I don't have the equations you're looking for, and I'm no longer sure how I'd go about deriving them. It's been too long since I took differential equations.

Reply

unixronin January 27 2014, 00:34:23 UTC
Velocity and acceleration are easy of course, and jerk is a pretty simple concept. I'm not sure I can come up with a practically usable understanding of jounce, let alone the remaining three.

Reply

unixronin January 27 2014, 00:36:07 UTC
I don't think you can just go from jerk and time directly to distance. You'd have to integrate under the curve.

Reply

kengr January 27 2014, 02:29:13 UTC
If it's *constant* jerk, then you can. Just like you can get distance from constant acceleration. My calculus isn't up to it, but someone whose calculus was up to it worked out the formula for me.

You *do* realize that derivatives and integrals can be calculated for various curves?

anyway, look at these formulas.

For constant velocity:
d=v*t

For constant acceleration
v=a*t
d=(a*t^2)/2

for constant jerk
a=j*t
v=(j*t^2)/2
d=(j*t^3)/6 (I looked up the formula in my notes)

Reply

unixronin January 27 2014, 05:39:42 UTC
Don't you think constant jerk is a bit of a special case though? When are you ever going to encounter it in the real world at any value other than zero?

Reply

kengr January 27 2014, 11:36:20 UTC
Constant *anything* is a special case.

But jerk is apparently constant enough in some situations for engineering types to have named it.

Reply


Leave a comment

Up