The momentum is calculated by multiplying the mass by the velocity. This can be translated into the following equation:
p = m*v
Therefore, at constant v, the momentum is directly proportional to the mass.
In other words, at constant velocity, the momentum increases with the increase of mass and decreases with the decrease of mass.
As for the inertia, it depends radially on the momentum where:
L = r * m * v
L = r * p where r is the radius.
