จาก
Serway, Moses & Moyer:
Modern Physics, 3rd Edition, ISE, 2005.
ISBN 0-534-40624-6 (paperback).
หน้า 149
รูปปกได้ที่
http://mpec.sc.mahidol.ac.th/forums/index.php/topic,154.45.htmlAn electron with kinetic energy less than 100 ev collides head-on in an elastic collision with a massive mercury atom at rest.
(a) If the electron reverses direction in the collision (like a ball hitting a wall), show that the electron loses only a tiny fraction of its initial kinetic everyg, given by
where

is the electron mass and

is the mecury atom mass.
(b) Using the accepted values for

and

, show that

and calculate the numerical value of
