Moment of Inertia of half disk

[Brad123]

Hello, just found this forum didn't know it existed. hopefully someone can help with this.

I am trying to figure out the mass moment of inertia for a half disk spining around the center axis. A full disk is I=1/2*M*R^2. Would the inertia for spining a half disk around the center axis just be half of this? Not homework, something I am working on.

Hopefully someone here can help

[Doc Al]

I am trying to figure out the mass moment of inertia for a half disk spining around the center axis. A full disk is I=1/2*M*R^2. Would the inertia for spining a half disk around the center axis just be half of this?
Yes.

Just to be clear: The formula will be the same, but since the mass is halved, the moment of inertia will be halved.

[Brad123]

Thanks for the quick responce. What was confusing me was that the half disk is rotating around what is the center (not COG) I thought it might get more complicated due to the rotation not being through the COG. thanks just 1/2 the formula for a full disk because it is half the mass. Here is an image for reference. Apreciated. (I am ignoring the small attachment point for simplicity)