Re: operational F, m, and a

[Robert Cohen <Robert.Cohen@PO-BOX.ESU.EDU>]

1. Why does v=dx/dt?

A. Because v is defined that way.
B. Because that is the way nature is.
C. Both A and B.

2. Why does F=ma?

A. Because F is defined that way.
B. Because that is the way nature is.
C. Both A and B.

I assume we all agree that the answer to #1 is A.  What about #2?
Operationally, we might calculate the force by using m*a but does that mean
the answer to #2 is A also?  The answer seems clear to me but I'm not sure
who agrees with me - people seem to be using different definitions of
"definition" (no pun intended).

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| Robert Cohen               Department of Physics       |
|                            East Stroudsburg University |
| rcohen@po-box.esu.edu      East Stroudsburg, PA  18301 |
| http://www.esu.edu/~bbq/   (570) 422-3428              |
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> -----Original Message-----
> From: Michael Edmiston [mailto:edmiston@BLUFFTON.EDU]
> Sent: Tuesday, October 16, 2001 5:25 PM
> To: PHYS-L@lists.nau.edu
> Subject: Re: operational F, m, and a
>
>
> Yes, the difference between defining units and defining
> concepts is clouding
> the issue.  I didn't intend to do that.  I went to NIST and
> IUPAP etc. to
> see if these people ever tried to define the concept of
> force; I already
> knew they define the unit of force.  But I think some of
> these organizations
> attempt to describe the concept of force also.
>
> Yes, it is possible to develop a concept of force that does
> not involve
> acceleration.  Jack described a concept development using gravity and
> equilibrium measurements.  I might quibble with the idea this does not
> involve acceleration by mentioning general relativity, but I
> won't go there
> anymore than I already did.
>
> I guess what I don't understand it why some think development
> of the concept
> of force via F=ma is so bonkers.  I have a concept of mass.  I have a
> concept of acceleration.  Why can't I develop a concept of
> force as that
> thing necessary to make a mass have acceleration?  I say...A
> net force is
> necessary to make a mass have acceleration.  You say... Oh,
> what's a force?
> I say... That thing you did to the mass to make it accelerate.