0
According th o this law if net force acting on an isolated system is zero then linear momentum remains conserved.
i.e. momentum just before the instant considered is equal to momentum after.
But we should be cautious in selecting the isolated system, and we can choose any number of objects as a system to apply this law on which resultant of all the forces acting is zero.
Then P1=P2.
This law is beneficial as it helps to calculate force, Impulse, the velocity of the objects and other related terms in the phenomena involved.
So this is one of the fundamental law of physics.
Note. Either no force is acting then net force is zero, or vector sum of forces on the system considered is zero.
