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# There's no such _thing_ as a weight

## There's no such _thing_ as a weight - Physics Forum

### There's no such _thing_ as a weight - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.

#31
03-30-2005, 04:25 PM
 TripleEight Guest Posts: n/a
There's no such _thing_ as a weight

"Don1" <[Only registered users see links. ]> wrote in message

Theoretically any effect of the gravitation fields never reaches absolute zero.
Humankind hypothesized that the universe is endless and boundless so that means
at an infinite distance from any planetary bodies the gravitational effect can
be assumed to have no effect on any matter.

Using this basic physic principle which I know you should have seen,

F = (G * m1 * m2) / r^2

F cannot be zero unless no other body (say m2 = 0) apart from itself (m1) exist.

lim [F, r -> infinity] = 0

#32
03-31-2005, 06:37 AM
 Morituri-|-Max Guest Posts: n/a
There's no such _thing_ as a weight

"Don1" <[Only registered users see links. ]> wrote in message

Which is why it would be a bad thing to say weight is an inherent property
of matter.

Thanks PD

#33
03-31-2005, 12:56 PM
 Don1 Guest Posts: n/a
There's no such _thing_ as a weight

Morituri-|-Max wrote:
SNIP<
property
If force, weight and inertia aren't inherent properties of matter, then
what are the inherent properties of matter? What other properties are
there for matter besides 3D bulk and density?

Don

#34
03-31-2005, 03:50 PM
 PD Guest Posts: n/a
There's no such _thing_ as a weight

Don1 wrote:
then

First of all, you have to distinguish intensive properties and
extensive properties. Very roughly, extensive properties depend on the
object as well as the stuff it's made out of. For example, two ice
cubes can have different volumes even though they're made from the same
stuff. Intensive properties have to do with the stuff itself,
independent of the actual object that contains the stuff.

Categorized this way, density is an intensive property and mass is an
extensive property, because two lumps of gold will have the same
density but quite likely different masses.

Now you can talk about various properties:
Extensive properties:
Volume
Mass
Net electric charge
Baryon number
Lepton number

Intensive properties:
Bulk compression modulus (liquids and solids)
Young's modulus (solids)
Temperature
Density
Concentration
Index of refraction
Conductivity
Permittivity
Permeability

and so on.

#35
03-31-2005, 05:59 PM
 TripleEight Guest Posts: n/a
There's no such _thing_ as a weight

"PD" <[Only registered users see links. ]> wrote in message

So intensive properties are always ratios? ie. mass per unit volume. Please
explain the temperature property. Thanks!

I remember I came across intensive and extensive properties in my first year
engineering course but didn't understand it well enough : |

#36
03-31-2005, 06:46 PM
 PD Guest Posts: n/a
There's no such _thing_ as a weight

TripleEight wrote:
inherent
are
the
same
an

Not necessarily. You could also look at it that one extensive property
is the product of an extensive property and an intensive property.
E.g. mass = density x volume.
There is no reason to think of density as more *derived* than mass or
volume.
Indeed, density is detached from the extensive properties because it
"belongs" to the stuff only and not how much of the stuff is there.
That is, I know the density of gold without having to know how much
gold I've got.

Here's another case: If you have a cable under load, it will stretch.
How much? Well that depends on:
a) how much load there is
b) how thick the cable is (cross-sectional area)
c) low long the cable is
d) what the cable is made out of.

Thus the stretch depends on three extensive properties and one
intensive property.

And we write that as dL = (L/Y)*(F/A).
where dL is the stretch and L is (c), F is (a), A is (b), and Y is (d).

Now you could also write this as Y = (F/A)/(dL/L), but I don't think
that tells you intrinsically anything more about the nature of Y.

Umm. Think of temperature as an index that describes the way that
energy will spontaneously flow between two bodies of different
temperatures.

first year

#37
03-31-2005, 07:33 PM
There's no such _thing_ as a weight

"TripleEight" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ].uk...

average kinetic energy per particle

#38
03-31-2005, 08:05 PM
 TripleEight Guest Posts: n/a
There's no such _thing_ as a weight

news:[Only registered users see links. ]...

Ahh of course...thanks for making it explicit.

 Tags thing , weight

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