If the net external force acting on a system is zero , then the total momentum of the system is zero

FALSE

Explanation: Momentum is the product of the mass of an object and the velocity of that object,momentum is a vector quantity which means it has a Magnitude (distance covered) and Direction.

Force is the product of the mass of an object and its acceleration,Force can also be described as the weight of an object after the force of gravity acts on its mass.

If the net force acting on an object is zero it does not mean that the momentum of that system is zero, because momentum does not solely depends on forces,it has to do with the MASS of the object and the VELOCITY of the object.

it is called kinetic energy

increase masses, decrease separation