/*******************************************************
* Calculate relativistic mass and speed of an electron *
* accelerated in an electron gun                       *
* ---------------------------------------------------- *
* SAMPLE RUN:                                          *
*                                                      *
* Give electron gun voltage in volts: 1e6              *
*                                                      *
* Relativistic mass (kg) and speed (m/s):              *
*  2.693395e-030  2.821249e+008                        *
*                                                      *
* ---------------------------------------------------- *
* Ref.: "Problem Solving with Fortran 90 By David R.   *  
*        Brooks, Springer-Verlag New York, 1997".      *
*                                                      *
*                  C++ Release By J-P Moreau, Paris.   *
*                         (www.jpmoreau.fr)            *
********************************************************
!Explanations:
!------------
!
! An electron accelerated by a voltage V in an electron gun
!
!                              2     2
! acquires an energy of Ve = mc - m c,  where
!                                  0
!                                        -19
!  charge on an electron   e = 1.602 x 10    coulomb
!
!                                         -31
!  rest mass               m  = 9.109 x 10    kg
!                           0
!                                         8 
!  speed of light          c = 2.9979 x 10  m/s
!
! The speed v of an electron of relativistic mass m (kg) is
! obtained from
!                                          2
!                 m/m  = 1 / sqrt(1 - (v/c) )
!                    0
!
!----------------------------------------------------------*/
#include <stdio.h>
#include <math.h>

  double Sqr(double x) {
    return (x*x);
  }

void main() {
 
  double rest_mass, rela_mass;  // kg
  double voltage;               // volt
  double speed;                 // m/s
  double e;                     // electron charge in coulomb
  double c;                     // speed of light in m/s

  e=1.602e-19; c=2.9979e8; rest_mass=9.109e-31;

  printf("\n Give electron gun voltage in volts: ");

  scanf("%lf", &voltage);

  rela_mass = (voltage*e + rest_mass*c*c) / (c*c);

  speed = c*sqrt(1.0 - Sqr(rest_mass/rela_mass));

  printf("\n Relativistic mass (kg) and speed (m/s):\n");
  printf("  %e  %e\n\n", rela_mass, speed);

}

// End of file rel_mass.cpp