Question

What is the momentum of an electron traveling at $0.980c$?

Final Answer

$1.35\times 10^{-21}\textrm{ kg}\cdot\textrm{m/s}$

### Solution video

# OpenStax College Physics, Chapter 28, Problem 36 (Problems & Exercises)

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Video Transcript

This is College Physics Answers with Shaun Dychko. An electron is traveling with a speed of 0.980

*c*and the question is what is its relativistic momentum? That's going to equal the Lorentz factor multiplied by the electron's rest mass multiplied by its speed. So that's*mu*divided by square root 1 minus*v squared*over*c squared*when you replace*γ*with 1 over this denominator. So that's 9.11 times 10 to the minus 31 kilograms— rest mass of an electron— times 0.980 times the speed of light— 2.998 times 10 to the 8 meters per second— divided by square root of 1 minus 0.980*c*squared over*c squared*and that's 1.35 times 10 to the minus 21 kilogram meters per second.