The momentum of a fast object compared to that of a slow object even if they both have the same mass, is their velocities.
Having same mass but different velocities results in different momentum.
Example: mass = 10kg
Velocity 1 = 50 Velocity 2 = 100
Momentum 1 = 10×50 = 500 Ns
Momentum 2 = 10×100 = 1000 Ns
Hope it helped!