Re: da/dt = jerk?

[Doug Craigen <dcc@ESCAPE.CA>]

> Am I missing something here?  If I am, I'd appreciate someone giving me
> the appropriate "jerk" vs. da/dt relationship.

As I understand it, da/dt is the definition of "jerk" in  physish.  As
such, one must be careful not to confuse it with the english word
"jerk".  When we lose the distinction betweeen english and physish, the
result is gibberish.

In physish, so long as acceleration is changing, there is a "jerk" (and
possibly "snap, crackle and pop" as well - the next few derivatives)
whether the change is abrupt or not.  So for example, an object bouncing
up and down on a spring has a jerk which is 180 degrees out of phase
with its velocity.  It is only at the top and bottom of its motion that
the jerk is zero (the very spots that an english speaking non-physicist
would be most likely to have said they would expect a "jerk" - since it
is changing direction there).

In the car example you give there is a jerk which is short-lived and
which is "felt" differently by the driver and the car.
()-()-()-()-()-()-()-()-()-()-()-()-()-()-()-()

Doug Craigen
          Latest Project - the Physics E-source
          http://www.dctech.com/physics/