# Why relativistic momentum equals the following?

In a solution to a problem we were given, it is written that a positron momentum with energy of 2mc2
(where γ=2) is √(γ2-1)*mc = √(4-1)*mc = √3*mc

How did they get that P=√(γ2-1)*mc?

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## Answers and Replies

Nathanael
Homework Helper
You are familiar with p = ϒmv right?
And also with ϒ = 1/√(1-(v/c)2) right?

Eliminate v from the two equations and what do you get?

Foruer
What I get is the answer thank you

Orodruin
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
2021 Award
While it gives you the right answer, it is much simpler to use the energy-momentum relation ##E^2 - p^2 c^2 = m^2 c^4## and just solve for ##p##.

Nathanael