00:01
So in this problem we can evaluate moments of inertia.
00:03
We have two masses of mass m on a thin bar that's massless, so we don't need to consider this bar other than its length, which makes it convenient.
00:13
And they have some radius or length, usually what we called, but we have r here so we keep the notation, but length r.
00:24
And we have two axes to consider.
00:26
The typing formatting got a little weird.
00:29
So we have two axes perpendicular to the bar through the center, and this is, i'm going to call the a -axis, and then perpendicular through the bars, but at one end, this is going to be the b -axis.
00:43
So the only moment of inertia equation we need is of a point mass, where we know that moment of inertia is equal to the mass of the mass times the radius it is from the axis squared.
00:55
Now even if this is a real spherical mass, as long as the center, if it's small in the center is at whatever radius this equation works.
01:07
So in a we need to consider, we don't need this in red, so for the moment of inertia of a we need to consider both masses.
01:19
So we need to put a 2 because the equation is going to be the same, they're symmetrical about each side...