# [PD] fft beginner question

Mathieu Bouchard matju at artengine.ca
Fri Dec 21 21:29:33 CET 2007

```On Fri, 23 Nov 2007, Martin Peach wrote:

>> So how do you measure the kinetic energy without calculating?
> You could measure the displacement of a spring that absorbs the
> collision.

By doing that, you are converting kinetic energy to potential energy in
order to measure it! You are assuming that specific displacements
correspond to specific amounts of potential energy that exist once there
is no kinetic energy left, at one point during the action of measuring,
when the object is stationary and the displacement is at its biggest.

>> So, where is the potential energy that allows atoms to fall apart?
>> Apparently it's stored as extra mass in the nucleus. If you snap a
>> uranium235 with a neutron, it becomes a krypton92, a baryum141 and
>> three neutrons. If you account the masses more precisely, which are not
>> the above numbers, you get:
> So, you can't measure the potential energy except by converting it to
> kinetic energy...

No, I'm saying exactly the opposite, it can be weighted, as it's part of
mass. Of course, weighting eventually involves some motion, but it doesn't
have to be like throwing something at high speed.

>> Which is 0.186033... some fraction of a particle. Why is it?
> You're forgetting the neutrinos which probably have a very small mass.

If scientists have that much trouble figuring out the mass of the
neutrino, it might be because it's so small that it possibly can't account
for any significant amount of this reaction. Anyway, a nuclear fission
reaction is very much known to emit *plenty* of energy :) which you can't
think of as being embodied by neutrinos because they very seldom interact
with any matter at all. Neutrino detection equipment is all buried deep in
the ground because the instruments are too sensitive, and they really need
to be that sensitive, because neutrinos are so close to undetectable.

_ _ __ ___ _____ ________ _____________ _____________________ ...
| Mathieu Bouchard - tél:+1.514.383.3801, Montréal QC Canada
```