🚀 go-pugleaf

>         I am in dire need of some (perhaps obscure) information. I need
> to know roughly how long it takes an automobile to stop at a stop sign
> from 40mph. I need to know the time of the stop as well as the dist. over
> which the negative acceleration took place.

No problem (and certainly not obscure)

A typical rapid, but nonpanic, deceleration might be half a "g."
Since 1 "g" = 22 mph/s this means the car will lose about 10 mph
every second.  So, want to stop from 40 mph?  Then give yourself
4 seconds,  ... from 60 mph?  ... 6 seconds, etc.

For the distance, just use average velocity times the time to stop
where the average velocity is half the initial velocity.  So,
for example

distance stopping from 40 mph = 20 mph x (4/3600) h = 1/45 mile
                                                    = 120 ft

Hope this helps.

John Mallinckrodt
Cal Poly Pomona
ajmallinckro@csupomona.edu