# Inertia in motion - why is momentum called this

1. Oct 31, 2009

### Kaxa2000

Inertia in motion - why is momentum referred to as this?

Also, what forces in nature are conservative does anyone know any examples?

2. Oct 31, 2009

### bp_psy

Referred as what?
All of them.

3. Oct 31, 2009

### Kaxa2000

Why's it referred to as "inertia in motion"

4. Oct 31, 2009

### bp_psy

The Linear momentum of a particle is defined as p=mv. It is a quantity that remains constant with respect to an inertial reference frame, if no forces act on the particle.

5. Oct 31, 2009

### Kaxa2000

It's also called inertia in motion

6. Oct 31, 2009

### bp_psy

I have never read or heard this anywhere. The only reason I see for somebody using this, is because mass is sometimes called a measure of inertia.If a mass is in motion it has momentum. I think it is an ambiguous and useless way to describe momentum. You should try to understand the usual definition.

7. Oct 31, 2009

### ideasrule

I've heard of momentum being referred to, metaphorically, as "inertia in motion". I don't think it's accurate, even as a lie-to-children, because it doesn't represent how hard it is to move the object.

8. Nov 1, 2009

### Phrak

This sounds like an old usage. Where did you read it?

9. Nov 1, 2009

### sganesh88

Inertia in motion alright. Inertia in what else? I have once read that "inertia" literally means laziness. Maybe this has got something to do with it.
Inertia would also be a fantastic name for a female. Wonder why no one has chosen it yet. :D

10. Nov 1, 2009

### Naty1

(a) somebody decided to call it that,
(b) somebody did not like momentum,
(c) somebody is pulling your leg. (fooling you)

Let's call it "floogum" from now on...

11. Nov 4, 2009

### gutti

if you look at angular momentum

angular momentum = moment of inertia x angular velocity

where moment of inertia is the distribution of mass

12. Nov 8, 2009

### tiny-tim

It isn't!!

(Unless you can produce a quote …)