Re: Newton's second law

[Justin Parke <FIZIX29@AOL.COM>]

In a message dated 11/6/2003 3:08:09 PM Eastern Standard Time, rlamont@POSTOFFICE.PROVIDENCE.EDU writes:

> The v in
> this case is the sideways speed of the sand, not the speed of the
> flatcar down the track - which remains constant because
> there is no
> force in this direction.
>
> Bob at PC

How do we know that "in this case" v is the sideways speed of the sand?  Sorry to sound so stupid...just trying to completely straighten out my thinking on this.

Justin Parke
Oakland Mills High School
Columbia, MD