Re: CAUSATION IN PHYSICS

[Robert A Cohen <bbq@ESU.EDU>]

On Sun, 15 Oct 2000, John Denker wrote:

> 0) To avoid misunderstanding and/or nitpicking:  Let specify that I
> interpret Leigh's statement to mean
>          Forces cause accelerations, and
>          not vice versa.
>
> See item (2) for more on this.
>
> [snip]
>
> ==============
> 2) The clarification in item (0) is important, because if somebody (e.g
> Robert A Cohen, 07:26 AM 10/15/00 -0400) takes the position that
>
> 2a)     forces cause accelerations, and by the same token
>          accelerations cause forces also...
>
> that's OK.  It's a slight stretch of the definition of causation, but I
> don't have a problem with that.  I have a slight preference for saying
>
> 2b)     force is proportional to (not the cause of) acceleration, and
>          acceleration is proportional to (not the cause of) force
>
> but the difference between version (2a) and version (2b) is too subtle for
> the average student.

Just for the record, I'd like to point out that I do not take the position
described by John in (2a).  I prefer (2b).  I'm not sure what I wrote in
my post that implied (2a).  All I wrote was that I agree that, for a cart
running into a car, one could write that the net force exerted on the car
is equal to the mass of the cart (not car) times the deceleration of the
cart (not car).  However, I don't think this is the proper way of
interpreting Newton's 2nd law.  I think it has the potential to confuse
students.

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| Robert Cohen               Department of Physics       |
|                            East Stroudsburg University |
| bbq@esu.edu                East Stroudsburg, PA  18301 |
| http://www.esu.edu/~bbq/   (570) 422-3428              |
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