## Essential University Physics: Volume 1 (3rd Edition)

We know that the mass is directly related to the rotational inertia, so doubling the mass doubles the rotational inertia. However, since the rotational inertia is directly related to the square of the radius, doubling the radius will increase the rotational inertia by a factor of 4. Using this, we have: $4 \times 2 = 8$