and here we normally call K12.

This has to be K21,

and this is K22, meaning that KIJ,

meaning the stiffness spring force or

stiffness acting on ice area

bounded due to the motion of J.

So, K11 is actually

the stiffness force acting on this mass.

I suppose to move this mass

by a little bit or unit or X1 in this way.

Then you can immediately see that there will be

[inaudible] acting on this way and KX1 acting on that way.

Therefore we can have over here 2K.

This is the stiffness matrix due to the motion

of this mass acting open over here.

So, I suppose move this mass by

unit then this will be elongated.

Therefore the force acting on this mass would

be K multiplied by m in this direction.

That is the direction same as the X1.

Therefore rearranging this I

have minus K. Now,

by the same token I have minus K over

here and I have 2K over here.

So that is what I obtain physical meaning

of this matrix formation.

I can see that this stiffness matrix

is symmetric because the system is a symmetric.

The mass matrix is also symmetric.