


Question
What is the amount of energy given off when an electron and a positron anhilalate?
Asked by: Bill Devenport
Answer
Using 9 x 10^{31} Kg. as the mass of each particle, and knowing that their combined mass
will be totally converted to energy, you can use Einstein's famous E = mc^{2} (where c = the
speed of light in vacuum = 3 x 10^{8} m/sec) to determine the total energy output of the electron/positron annihilation:
E = (mass of electron + mass of positron) x (speed of light in m/sec)^{2}
E = 2 x (9 x 10^{31})kg x (9 x 10^{16})m^{2}/sec^{2}
E = 1.6 x 10^{13} kg m^{2}/sec^{2} = 1.6 x 10^{13} Joules
Answered by: Paul Walorski, B.A. Physics, Parttime Physics Instructor

