The distance doesn't depend on the mass.
a moving objects momentum
That is called speed or - if the direction is relevant - velocity.
keep distance with moving objects.
Momentum
No. Velocity is a vector that describes both the direction in which an object is moving and its speed in that direction.
Momentum depends on mass and velocity.
momentum
uniform motion
When all forces are balanced, the object can either be moving at a constant velocity or be at rest. But because you asked for balanced forces on a moving object, it is moving at a constant velocity.
If you have no velocity, then you aren't moving.
They would be traveling at the same speed. Two objects moving with the same velocity must be moving in the same direction and at the same speed. The reason for this is because velocity is speed in a specified direction. Another way to say that is to say that velocity is speed with a direction vector. It is a physical quantity with magnitude and direction. Two objects moving with the same speed could be moving toward a head-on collision. Or they could be moving along convergent, divergent or skewed paths. Not so with two objects that have identical velocities. They are moving on the same or on parallel courses, and they are moving at the same speed.
The property you are looking for is the objects momentum. Momentum = Mass * Velocity.