# Cause of Momentum

1. Sep 13, 2011

### richerrich

What causes momentum? Are there some force carrier particles passed on from one object to another causing momentum?

2. Sep 13, 2011

### Naty1

Nobody really knows..... anymore than we know, for example, "what causes mass?".

But there are some insightful ways to summarize what we observe about it:

FT = mv = p, so you can see one set of "causes" ....mass times velocity....and is a convenient way to describe one common characteristic of mass.

In classical physics, momentum is closely related to inertia:

Inertia is the resistance of a mass to a change in its state of motion or rest; momentum is a measure of the energy of a moving mass. [These two terms might be interesting to compare in more detail]

In relativistic mechanics, things change a bit but don't give me (personally) any better insights....momentum involves the Lorentz factor and invarient mass. The only other helpful thing I can think of is that momentum is frame dependent...two different observers will not in general observe the same momentum....they see such energy differently.

3. Sep 13, 2011

### richerrich

Thank you :)

4. Sep 13, 2011

### Nihilist

It's just a transfer of energy. Object A is traveling and Object B gets in the way, they bounce into each other, vibrate a little and the magnitude of all the tiny vibrating vectors takes the objects in their respective ways. No particles exchanged, only vibrations, some maybe thrown away and mixed up on the surface but there are no 'force carrying particles' moving from one to the other.