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

["D.V.N. Sarma" <dvnsarma@gmail.com>]

When a real body attains the acceleration a=F/m it will be in a deformed
condition.
The regions closer to the point of application of force will be having
greater compression
than the regions at the free end. This deformation also takes finite time.
The situation can be visualized by point masses connected by springs.
But this deformed state so attained will be changing in time as the
longitudinal wave is reflected back and forth unless a standing wave is
formed.

Hope I have got it right.

regards,
Sarma.

On Wed, Dec 8, 2010 at 2:27 AM, Bernard Cleyet
<bernardcleyet@redshift.com>wrote:

> Nope, at least not here.   The C of M moves toward the point of the applied
> force until the shock wave reaches the new position of the C of M.
>
> bc thinks this is shown by the golf ball pics.
>
> http://www.springerlink.com/content/936p5m7481450164/fulltext.html
>
>
> note: using the concept C of M implies not a point (a mythical construct),
> but a macroscopic or extended object.
>
>
> On 2010, Dec 07, , at 11:03, LaMontagne, Bob wrote:
>
> > ?? Hadn't we established that the acceleration of the center of mass
> begins at the moment that the force is applied and follows F = m a(cm)?
> > Bob at PC
> >
> > ________________________________________
> > From: phys-l-bounces@carnot.physics.buffalo.edu [
> phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Philip Keller [
> PKeller@holmdelschools.org]
> > Sent: Tuesday, December 07, 2010 1:13 PM
> > To: 'Forum for Physics Educators'
> > Subject: Re: [Phys-l] FW: The "why" questions
> >
> > Suppose I apply a force to a real body and I am interested in the physics
> of that finite time interval before a = f/m.
> > How do I know that I have applied a force?  In fact, what IS a force?
>  Halliday and Resnick takes the same approach as Young and Freedman (and
> others I'm sure):  begin by saying a force is a push or a pull, but then
> continue with an operational definition: "To measure such forces
> quantitatively, we express them in terms of the acceleration that a given
> standard body experiences in response to that force."  (H & R, I'm looking
> at the 4th edition)
> > So my question is:  if an object is in equilibrium and then I come along
> and apply a force (or so I believe), until the object accelerates, how do I
> know the force exists?  Or is the operational definition to include the word
> "eventually"?
> > > -----Original Message-----
> > > From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> > > bounces@carnot.physics.buffalo.edu] On Behalf Of D.V.N. Sarma
> > > Sent: Monday, December 06, 2010 9:12 PM
> > > To: Forum for Physics Educators
> > > Subject: Re: [Phys-l] FW: The "why" questions
> > >
> > > For real bodies a = F/m is acquired only after
> > > a finite interval of time.
> > >
> > > regards,
> > > Sarma.
>
>
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