The momentum of an object is calculated by the following formula:

Momentum (p) = Mass (m) × Velocity (v)

Since the mass is not moving, its velocity (v) is 0.

Therefore, the momentum of the 500 kilograms mass is:

p = 500 kg × 0 m/s = 0 kg m/s

So, the momentum of a 500 kilograms mass that is not moving is 0 kg m/s.