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Re: Problem



Michael Edmiston wrote:
... If
v at the top is zero, and if a is zero or undefined, how does it get
back
down?

The acceleration (the vector a) is well defined and equals -g throughout
free fall - even in the vertical case. It is the derivative of the speed
(d|v|/dt) that becomes troublesome at the peak of a vertical free fall.

This is an example of the limitations of human mathematical models.
Continuum mathematics (calculus, etc) falters in describing the time
behavior of the speed and its derivatives, in this case. It is good that
there are such examples - to remind us that our models (both mathematical
and conceptual) are faltering human constructs.

Bob Sciamanda
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor