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

[John Denker <jsd@av8n.com>]

Michael Edmiston wrote:

> I think that if forces can exist without acceleration, but acceleration 
> cannot exist without forces, students will view the force as more 
> fundamental and/or the net forces can be the cause of acceleration.  I 
> thinks it's hard to say that acceleration can be viewed as the cause of 
> forces when it is clear forces exist without acceleration.

That's just wrong physics.

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.

> I think the person who first mentioned this got pushed aside on a 
> technicality.

The point here is consistent application of the laws of physics.
I think that ranks quite a bit above a mere technicality.