i think that the force by which an object is accelerated determines its speed apart from its mass.
as acceleration is directly dependent on the force applied.
for ex- if an object of less mass is pushed with a force of 10N and a heavier object with a force of 15N then...
according to me the answer of this is the mass of the 2 objects.
if the mass of one of the magnet is less than that of the other one then it will atteacted towards it with a great force and will repel with a smaller force