Inertia and Physics- was "Key Inertia"

[Paul Chick]

Richard,

I think I see where you are coming from on this one.....I am focusing on the
the part of Don's statement of UNITS of "inertia" as being that since there
are no units for inertia, more of nothing is still nothing.   You are saying
that those are two separate statements:  There are no units of inertia.  And
one object cannot have more inertia than another.  I apologize.....not being
able to communicate in person is a barrier.  Am I understanding you
correctly????

>
> Don G said
> " There are no units of "inertia"; one object cannot have more "inertia"
> than another. "
>
...

Paul Chick continues
"Following that, everything that you quote (except for what the PhD
says) is saying exactly the same thing."

Again Paul... seems to me the two statments below say exactly the same
thing... except that Calin doenst get into torque.

> Don G said in another post
> "Inertia is just the stubborn tendency of matter to resist change .....
> It resists in the form of force (or torque, for a rotating object)"
>

Force is directly related to mass, so if there is an increase in mass, there
is an increase in force.  If there is more mass, there is more inertia.
Agreed?  Example:  if you increase the amount of mass of an object, it will
take more force to get the object to move.  A heavier hammer requires more
force (pushing down on the key) to make it move.  It is also true that the
heavier hammer has more inertia.  For a rotating object instead of force,
torque is used.

> Calin Thomasen said today
> "Any object has a quantifiable resistance, impedance if you prefer, to a
> change in its velocity to any other given velocity, and that  resistance
> is reflected clearly and precisely in the amount of force required to
> achieve that acceleration."

If resistance or impedance are used to define inertia, fine.  Then according
to F = ma if you increase the mass, force will change.  One can also argue
that according to the equation if you increase acceleration you can increase
force, thus, because acceleration is a change in velocity, a change in
velocity also affects force.  Well, if this is true, what happens when an
object is at rest.  Acceleration and velocity are zero.  Does the object not
have inertia?  Looking at the definition of inertia as the "tendancy" of an
object not to change its motion (this case zero motion), which in physics is
the accepted definition, an object at rest has inertia.  I always ask my
students "Why does a magician use fine china for the magic trick of pulling
a table cloth out from under the table setting".  The answer is because fine
china has more mass (it is heavier) than regular, cheaper, everyday dishes.
The magician will be more successfull because the non-moving fine china has
more inertia (tendancy not to move) than does cheaper everyday dishes.
Because non-moving objects still have inertia, it is accepted in physics
that velocity and acceleration do not effect inertia nor are they affected
by inertia.  Because force is directly related to mass, it is misconceived
that in a round-about way acceleration (and velocity) are affected and they
have an effect on inertia because force effects acceleration.  It's not a
two-way street.  An increase in mass -> an increase in inertia.  Not: an
increase in inertia -> an increase in mass.  An increase in mass ->
(requires) an increase in force.  Not: an increase in force -> an increase
in mass.  These are reversible: an increase in force <-> an increase in
acceleration.  A change in acceleration <-> a change in velocity.


Paul Chick.