If the fly, or any object for that matter, is in contact with something, then don't they possess the same velocity?

I still say that in order for the fly to switch direction, it has to come to a complete stop.

Well, the train is stopping the fly from moving forward, so for a split second, (if the train is in contact with the fly) the train has to be going zero mph.

I've not found someone that can explain this and I go cross-eyed thinking about it...lol

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