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Authored by: Anonymous on Saturday, September 15 2012 @ 12:53 PM EDT |
Anonymous wrote:
I have seen it written that if the train is running at 100
mph (140 kph) then the driver must start the process 5 miles (8 km) away from
the desired stopping point.
This is for normal stops so emergency stops
would be a little less (but undependably so for reasons posted by others),
however allowing for signal placing might increase beyond that.
The elementary physics answer is that stopping distance goes with the
square of the speed. So if your first statement is correct, the stopping
distance from a more reasonable speed (at least in the US) of 50 mph would be
1.25 miles (1/4 of 5). This assumes a constant stopping force, brakes not losing
effectiveness as they heat up, etc.
(The basis is that an object's
energy is proportional to the speed squared. Also, energy is proportional to
force x distance. So the distance over which the brakes supply the force goes
with the speed squared.)
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