Why must the axis of rotation pass through the center of mass?

[glen_ky]

1) When we use the equation of L=(moment of inertia)*(omega) to calculate the angular momentum of a rigid body rotating around a moving axis, why the axis of rotation must pass through the centre of mass of this body and the axis should also be a symmetrical axis?

2) If for a fixed and non-moving axis, is this necessary to pass through the centre of mass?

Pls help, thanks.

 

[glen_ky]

If someone could help...pls...Thanks...

 

[glen_ky]

Why nobody can help~~~how dissapointed...haizzzZzzzz...

 

[rcgldr]

Moving axis? How is the axis moving?

You can calcultate an angular momentum about any real fixed (relative to object) axis, but it the object is "free spinning", then it has a "natural" axis.

Maybe wiki will help here:

http://en.wikipedia.org/wiki/Angular_momentum