The formula for momentum based on the law of conservation of momentum is as follows,

P=mv

Here, m is the mass of the object and v is the speed of the object.

In the above formula, momentum P is said to be conserved.

In modern physics, the first law of relativity states that in all inertial frames the laws of physics are the same. Therefore, the relativistic momentum is conserved in modern physics is as follows,

P=γmv

Here, γ is the relativistic factor and at low velocities value of relativistic factor is equals to 1.