kill(all)$

van=facebook.com/LearningCalculus$

      Calculate the life time of the neutral pion particle.
      The decay width Gamma of the π0 expressed in units of electron Volts is: 

Gamma: 7.7 * eV;

      The lifetime tau is 1/Gamma:

tau: 1/Gamma;

      The conversion factor from eV to seconds is:

secondsToElectronVolts: 1/(1.52 * 10^24 * 10^9) / (s*eV);

electronVoltsToSeconds: 1/secondsToElectronVolts;

tau * electronVoltsToSeconds;

p(u):=-%i*del(u);

E^2 = p(x)^2 + m^2;

p

del(del(x));