"An object in motion..." joke

This story was related to me yesterday at lunch by a fellow manager, who
heard it from his dad (guaranteed true...) Phenomenal testimony that
physics shall not be denied, with some small humor value as well.
This story involves railroad cars, Denver and a fascinating gadget used in
auto wrecking yards called a "chipper." Apparently this device is fed
old auto carcasses, and it in turn produces manageable-sized "chips" of
metal.
Seems that on this eventful evening, four gondola cars were filled by a
chipper and headed out of Denver around dusk. Somewhere along the track,
on an uphill grade, something mechanical failed on one of the cars, and
the train pulled to a siding to uncouple it. The dutiful crew chocked
the wheels with rocks, wood chunks, etc. and then proceeded to unhook the
car.
Seems no one had the slightest idea of the mass being packed in that unit,
as the rocks/wood held it in place for about 6 seconds. Since the crew
had not yet re-switched the tracks (they thought the rest of the train would
be returning to the main line) the gondola car soon found itself back on the
main trackline, heading back into Denver.
The engineer sprinted to the engine and full-throttled the thing after the
car. After 15 minutes, he still didn't even have a visual on it, so he
abandoned the engine, flagged down the nearest car, and drove to the
nearest station, from which he radioed the situation that this car was
cranking toward town and no one knew exactly where it was.
The station crews immediately calculated the correct combination of switches
to route this car on the straightest course thru Denver, the rail yard, and
out the other side, then remotely downed every crossing gate they could,
followed by dispatching crews, cops and civil servants to down the rest
of the crossing arms manually and staff the intersections.
Several witnesses testified that the gondola car passed their locations at
between 85 and 90 MPH.
Whilst traversing the rail yard, the car was forced to execute a slight
left-hand curve in the track on its way out of Denver. The "post mortem"
revealed that the curved section of track was "stretched" and displaced
8 feet to the right by the car.
Immediately upon leaving the yard, two of the fastest engines they had were
dispatched, full-throttle, in hot pursuit of the errant gondola car.
Since dusk had now turned into evening, no one could get a visual on the car,
but it did proceed out of Denver until it hit yet another uphill grade, at
which time the pendulum effect took over...
The drivers of the engines (serially-coupled) suddenly saw a dark blob
approaching them on the track, They quickly (?) slammed the engines into
reverse, but could see after about a minute that they were not gaining
any ground on this car, so they jumped from the cab.
One of them, looking back at the impact, noted that, although the mass of
the two engines was sufficient to stop the car, the front coupling assembly
of the lead engine was obliterated, and the front engine was "lifted in
place and set back down" by the impact.
Steven Swinkels (with thanks to Michael Andrews for the tale)
Amdahl Corporation