Originally posted by

**Da Pope**View Post**correspond to any real number**. Classically, this is the same thing as saying the rebound distance is 0. This is naive, however, and leads directly to the contradiction "This object, which can not deform, is storing 25J is an internal vibratory (deformational) state." Remember that I am not the one that sets up physics problems like the one I mentioned; I am not the one telling students, collegues, or whoever that energy missing from the KE calculation is to be found in the (deformational) internal states of the object, while the object is rigid and can't deform.

**Physicists are.**I did not invent the idea of rigid body inelastic collision, I just pointed out that there is a paradox implied, and asked you to take a stab at resolving it.

The resolution of the paradox requires us to be precise about what we mean when we say "An object is perfectly 'rigid' when it can not deform in any way." So, let us say instead "An object is perfectly 'rigid' when, for every pair of points on or inside its perimeter, the distance between them

**remains constant**with respect to time, where "remains constant" means 'does not differ by any real-number amount.'

As I pointed out the question doesnt make

**any**physical sense.
On the one hand you say deformation cannot happen and then later (

**after it being pointed out in my earleir post**) claim it does due to an increase in internal energy.
Your intellectual

*Gong Sau*was at best a badly poised high skool example used to teach a concept in a grossly oversimplified way.Since you're more interested in claiming the question is stupid because there is an apparent paradox in play, than in attempting to resolve it, I'll do the work for you:

If we think for a moment of highly (but not perfectly) 'rigid' objects as doing all of their deformational work in the form of a "ring" of certain pitch, for objects of differing 'rigidity' but identical mass, that ring will tell us the deformational energy resulting from a collision in terms of it's period/frequency/pitch. As the

*deformability*(defined as the maximum difference two points on the object may display) of the colliding object becomes vanishingly small, so does the frequency of the "ring". An object with infinitesimal

*deformability*is called (perfectly)

*rigid*, and any "missing" energy will be found in the infinitesimal frequency (and amplitude) of its ring.

Another way of stating this is that the slope of the stress-strain curve approaches infinity as deformability goes to zero.

As they say, :owneddanc

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