(adsbygoogle = window.adsbygoogle || []).push({}); problem:

three equal masses connected by light rods, the masses are positioned at (a,0,0), (0,a,2a) and (0,2a, a) now i work out all the products, and moments of inertia to get the inertia tensor, the thing that is baffling me is how you can have Ixx = 10ma^2, with all off diagonal products of x (Ixy, Ixz,) equal to zero. this clearly shows that one of the principal axes is the x - axis, but i dont see how this can be the case when the centre of mass clearly doesnt lie on the x axis(im picturing a triangle with a point on the x axis, and its base in the zy plane). unless this result simply means one of the principle axis is parrallel to the x axis?

its just kinda weird

help?

i actually get the right answers, and i understand that for the rest of the tensor (Iyy, Izz, Iyz) its a diagonalisation problem to find the other principle axes for this shape/orientation. its just i have issue with the physical meaning of what going on here with the x axis.

cheers

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Principal axes/inertia tensor

**Physics Forums | Science Articles, Homework Help, Discussion**