velocity of daughter nucleus

Discussion in 'Physics' started by circuit2000, Jun 3, 2007.

  1. circuit2000

    Thread Starter Active Member

    Jul 6, 2006
    1)Determine the maximum possible speed of the daughter nucleus in negative beta decay of a He(6,2) nucleus which is initially at rest.
    I solved in the following way:
    He(6,2) --> Li(6,3) + electron + antineutrino
    The daughter nucleus will have maximum speed when the electron and antineutrino has zero kinetic energy. Applying mass-energy equivalence,
    M(He)c^2 = M(Li)c^2 + K(Li)
    Where M(He)=atomic mass of helium isotope, M(Li)= atomic mass of Lithium isotope,
    K(Li)=Kinetic energy of daughter nucleus
    On simplification I get,
    K(Li)=3.52 MeV
    (1/2)M(Li)v^2=3.52 MeV
    On simplification I get,
    v=1x10^7 m/sec
    But the answer given in my book is 1x10^5 m/sec. Could someone please tell me where I have gone wrong?
  2. recca02

    Senior Member

    Apr 2, 2007
    i think its because u took ke of electrons as zero (its ok to take that for neutrinos and antineutrinos i believe ) .
    try solving using conservation of momentum and energy.