Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: g

Tim O'Donnell writes:
-----Original Message-----
From: Tim O'Donnell [mailto:odonnt@CELINA.K12.OH.US]

No negative time is allowed; I think that would mean we are going
backwards in time.

Not necessarily. Negative times could easily come from a quadratic solution
to a projectile or free-fall problem. Consider y = H - 1/2 g t^2 , with the
statement that the object is dropped at t = 0. In the solution of the
equation, there are two times when y = 0, one is "non-physical" since it
describes the motion of an object thrown upward from y = 0 at
t = -sqrt(2H/g), which just happens to be at the top of its trajectory at t
= 0.

*********************************************
"We especially need imagination in science.
It is not all mathematics, nor all logic,
but it is somewhat beauty and poetry."

- Maria Mitchell
*********************************************
George Spagna
Department of Physics
Randolph-Macon College
P.O. Box 5005
Ashland, VA 23005-5505
phone: (804) 752-7344
FAX (804) 752-4724
e-mail: gspagna@rmc.edu
http://www.rmc.edu/~gspagna/