Momentum
Momentum is the measure of 'how' much motion a body posses and is of prime importance to Mechanics,
Mathematically if we have a body of mass moving with velocity
then it's momentum
is defined as
The central importance of momentum is due Newton's second law which states or rather defines Force
acting on a body to be equal to it's rate of change of momentum.That is if
is the net force acting on a body then we have\
\
This means if a body moves such that it's momentum vector remains invariant with time then we can conclude that there is no net Force acting on it