Re: [Phys-l] Equations (causal relationship)

[Brian McInnes <bmcinnes@pnc.com.au>]

On 01/05/2006, at 1:35 PM, John Denker wrote:

> As surely as a set of force vectors can sum to zero, a set of
> acceleration vectors can add to zero.
>       F1 = m a1
>       F2 = m a2
>       F3 = m a3
>
>   (F1+F2+F3) = 0
>   (a1+a2+a3) = 0
>
> The F=ma law does not give any preference to F relative to a.

Separate and distinct forces can act on a particle.

The particle experiences one unique acceleration, not separate  
accelerations associated with each force.

Or, putting it slightly differently:  more than one force can act on  
a particle but a particle can only experience a single acceleration  
(which, of course, may be zero).

In relation to John Denker's words above,  I know what a set of force  
vectors acting on a particle is; I do not know what a set of  
acceleration vectors relating to a particle is.  I do know what a set  
of  vector components describing the acceleration of a particle is,  
but that is something different.

If what is written is a claim that when a particle has three forces  
acting on it there is a separate acceleration associated with each  
force, well, I just can't buy that.

Brian McInnes