Would you get at the same concept by reframing the original question as a
comparison question:
Given two simple pendulums of lengths L and L+delta, both passing through
their equilibrium positions at the same speed. Which has greater
amplitude?
This way, we don't haave to worry about the mechanism used to lengthen the
string.
As for the case where the lengthening occurs at the extreme point (where v
= 0), I don't see why the angular amplitude would be affected. It would
be like replacing the string with a longer string and then restarting the
oscillations, but still from the same angle. But the equilibrium speed
would increase.
Phil Keller
1st post to list -- hope it isn't gibberish :)