Re: Questions on Neg. and Pos. Acceleration

[Peter Vajk <vajk@IX.NETCOM.COM>]

> Date:    Thu, 23 Sep 1999 07:35:59 -0400
> From:    jmanor <jmanor@REMC4.K12.MI.US>
> Subject: Questions on Neg. and Pos. Acceleration
>
> 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?

This question has produced a lot of discussion on the pedagogy for
vectors and kinematics,  but NOBODY has given a simple, direct,
everyday, physical answer to the question:

> Is it possible for an object to have a negative acceleration while
> increasing in speed?
Yes,  if you put your car in reverse and floor it.

> And also can you explain if the velocity of an
> object be negative when its acceleration is positive?
Yes, if you are backing up and hit the brakes.

> and vice versa?
Yes, if you are driving forward and hit the brakes.

These questions, BTW, can be found at the end of Chapter 2 (Linear
Kinematics) in both Serway & Faughn "College Physics" and in Serway
"Physics for Scientists and Engineers."


Peter Vajk
St. Joseph Notre Dame High School
Alameda, CA 94501