Re: [Phys-l] The "why" questions

[Bernard Cleyet <bernardcleyet@redshift.com>]

I  suspect from your description I must correct my supposition on the a of the C of M.  Initially the a of the C of M is in the opposite direction to the applied force, as the position of the  C of M moves towards the first car.  The point at the initial C of M doesn't move 'till the sound wave (first car) reaches it.   

My prob. is that I think Mr. N thought points existed.  W/ that assumption N law is symmetrical.  Since points don't exist, I think N is not symmetrical.  There is always a delay tho it may be femto-seconds.

bc still naive?


On 2010, Dec 03, , at 05:50, Jeffrey Schnick wrote:

> Consider three mass m carts equally spaced at rest on a straight
> horizontal track.  You start pushing an end cart with a force of
> magnitude F toward the middle cart and keep doing so.  As soon as you
> start pushing, the center of mass of the set of three carts starts
> experiencing an acceleration of F/(3m) in the direction in which you are
> pushing even though the middle cart is experiencing no acceleration
> until the one you are pushing is bumping into it.