Calculating Rotational Inertia of a Disk with Mass M and Radius R

[kolua]

If there is a disk of mass M and radius R that is already rotating, then someone puts a block with mass m on it a meters away from the center of mass.
What is the rotational inertia then?

Is it I=(M+m)R^2?

 

[tommyxu3]

The moment of inertia is additive. The original moment of inertia of the disk should be $\frac{1}{2}MR^2$ and the block's is $m\cdot (1m)^2$ if it's small enough for us to ignore its volume. The answer should be the sum of above.