No but somehow it doesn't look like a fly cast. So what keeps the rail tracks in place?
Paul,
As Walter said there are no physical constraints like train tracks that would force the path of the fly to exactly follow the exact same path of the rod tip. I think that is a pretty obvious fact that you can see from high speed videos. Gravity seems to have its own say about these things.
I can now see that for the literally minded the train example was a poor analogy. I was just trying to point out that as long as there was a fixed length between the engine and the caboose then the caboose would have the same speed along its path at any point in time compared to the speed of the engine even though the caboose may be on a straight piece of track while the engine is going around a curve. I.e. thinking about comparative speeds not comparative velocities.
In regards to paths, a section of line will tend to follow the path of the line in front of it, so you will find the fly end of the line follows a path that is similar to the tip path. You can see that fact in high speed videos as well. Note I said similar not exactly the same.
The way I calculate the tip speed along its path is to measure the arc length of that path as function of time and then take a derivative of that length vs time function to get ds/dt speed curve along that path.
I have yet to see a video that tracks the tip path and the path of the fly in the same frame, but if one existed I am saying that you could calculate the ds/dt speed curve for the tip along its path and the ds/dt speed curve for the fly along its path and you would find that the two ds/dt speed profiles would nominally be the same.
That is assuming the length of line connecting the two remains constant and that line shape does have any slack or crazy shapes. But I think that for good casts the shape of the line between the rod tip and the fly while the rod tip is accelerating along its path (another derivative unfortunately) may not be straight, but is not full of twists and turns either.
So back to your original question,
what I'm asking is if the rod tip is still accelerating will this result in acceleration at the fly end?
The absolute value of the acceleration in the x and y directions will be different, but the acceleration of the rod tip along its path and the acceleration of the fly along its path (the derivative of similar ds/dt curves) will nominally be the same. So the answer to your question is yes.
Gordy