Question

An electron whose rest mass is 9.11x10^-31 kg moves with a speed of 0.8c. what is the kinetic energy

Answer 1

we know that relativistic mass = m = $\frac{Rest mass}{\sqrt{1 - \frac{v^2}{c^2}}}$

substituting rest mass = 9.1 × 10⁻³¹ kg and v = 0.8c

we get rest mass = m = 15 × 10⁻³¹ kg

we know that kinetic energy of moving electron = 0.5 × relativistic mass × v²

substituting the relativistic mass and v = 0.8 × 3 × 10⁸

we get KE = 4.32 × 10⁻¹⁶ {kg.m²}/s²