@bill93?ÿ
Yes. The fly has to fly faster than the trains or else it can never get started.
It's a cool problem because it has a simple solution and a complicated one.
?ÿ
You can't say how far the fly will travel until you know the speeds. Are you trying to set up the sum of a series? If so, you need more I formation.
The distance divided by the sum of train speeds gives time to collision. That time multiplied by fly speed gives the distance it travels.
How can you say it travels one mile?
At 20 mph for the trains and traveling a half mile each to the point of collision is the point in time when the fly will be squashed.?ÿ If it flies at double the speed of the trains for that period of time, it will travel twice the distance of each train, or one mile in this case.?ÿ If it flies four times faster than the trains, it will travel two miles.?ÿ If it flies six times faster than the trains, it will travel three miles.
Clearly nobody here has ever tried squishing a fly!
In any case the locomotive buffers will meet first, before the loco bodies collide. At 20mph that time-gap is more than the fly needs to buzz off out of the way.
Oh - and what sort of a mile is it. nautical, imperial, roman, egyptian?
Why is there even an International Foot? Who else still uses Imperial apart from the US?
Because the US still uses the imperial system a lot of places have to, in practice, for the benefit of the US market. And it's more than just soda bottles and dimensional lumber. It's also space ships to Mars and such.?ÿ
Before 1959 there were a lot more than 2 definitions of the foot, relative to the meter, in play. After the "international foot" was defined all those many definitions disappeared except the US Coast & Geodetic Survey's version of the foot, which survived only for use by surveyors only because of the USC&GS's legacy use for NAD27.
That legacy use should have terminated when NGS released NAD83, but weaker minds prevailed.?ÿ ?ÿNow we have another opportunity to stop the madness of having 2 versions of the foot.?ÿ The NGS has the ability to deprecate the US Foot. It is the only agency in the world that supports its use. It cannot deprece the international foot.
@bill93?ÿ
Well, I can say anything I want to say. As you pointed out, if the fly flies at twice the speed of the trains, it will fly one mile, so, obviously, the fly flies at twice the speed of the trains. I don't have enough information to solve the problem, but how can I make a given solution work?
A surveying analogy would be a least-squares solution that fails the chi-square test at the 10% level and the 5% level, but passes at 1%. If the surveyor accepts solution, then he's found a chi square level that makes his given solution work.
Food for thought at the least and a reason to question one's procedures at best.
Well maybe at least the idiot engineers that import international feet into Microstation and export US feet into autocad will stop screwing things up some day.?ÿ