# Is angular frequency absolute?

1. Mar 31, 2013

### tade

In classical mechanics, is the angular frequency of a rotating object, planetary system etc. the same as viewed from any inertial reference frame?

2. Apr 1, 2013

### Staff: Mentor

All reference frames can agree on a common clock, and all frames have a meaningful way to assign a direction to the object.
They have to agree on the center of rotation, but that should be easy for rotating solid objects, planetary systems and so on.

3. Apr 1, 2013

### 0xDEADBEEF

The key to the answer is whether the centre of rotation is part of your reference frame. If two objects circle each other around their common centre of mass the angular frequency of this rotation is independent of the inertial reference frame. If, on the other hand, you consider rotations around the origin of your coordinate system (something that is usually done in conservation of angular momentum calculations) then the instantaneous angular frequency will depend on the inertial reference frame.

4. Apr 1, 2013

### tade

I understand. thanks

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