What is the velocity of a 55 MeV alpha particle What is the

What is the velocity of a 5.5 MeV alpha particle. What is the ratio of its mass to its rest mass? What fraction of an old sample of Ra obtained from ^238 U is ^ 210Po? How-old is old?

Solution

4.

mass of the alpha particle: m = 4u = 4*1.67x10^-27 kg

kinetic energy of the alpha particle is,

   K = 0.5mv^2

   v = sqrt[2K/m]

      = sqrt{[2*5.5*10^6*1.6x10^-19]/[4*1.67x10^-27]}

      = 1.62e+7 m/s

ratio:

     m/m0 = (5.5 MeV/c^2)/(3,727.4 MeV/c^2) = 1.47e-3