Re: Questions on Neg. and Pos. Acceleration

[Uri Ganiel <uri.ganiel@WEIZMANN.AC.IL>]

At 7:35 -0400 23/09/99, jmanor wrote:
> Is it possible for an object to have a negative acceleration while
> increasing in speed?  And also can you explain if the velocity of an
> object be negative when its acceleration is positive and vice versa?


YES!
Imagine a body moving in the negative X direction, at a certain
speed, and having an acceleration along that same direction (i.e. the
acceleration is negative). Its speed will increase.
As to the second part of the question: again, an object moving along
a straight line to the left (say), while you define the direction to
the right as positive, will have a negative velocity. If the
acceleration is directed to the right, you have the situation you
asked about.

A-propos, positive acceleration with negative velocity, remember the
official who reported:
"We are making progress. Things are getting worse at a slower rate..."

Prof. Uri Ganiel
Head, Department of Science Teaching
The Weizmann Institute of Science
Rehovot 76100, ISRAEL

Phone: 972-8-9343894
FAX:    972-8-9344115

E-mail:  uri.ganiel@weizmann.ac.il