Question

A neutron moving with a speed of 10^6m/s suffers a head on collision with a nucleus of mass number 80.what is the fraction of energy retained by the nucleus

Answer 1

Conservation of the linear momentum and total kinetic energy, using relation, E = mc2 we can evaluate the energy of both particles before and after collision.

Collision between neutron and hydrogen atom will be inelastic if a part of kinetic energy is used to excite atom.

If u1 and u2 are speed of neutron and hydrogen atom after collision, then mu=mu1+mu2−−− (1) 12mu2=12mu21+12mu22+△ε--- (2) u2=u21+(u−u1)2+2△εm u21−uu1+2△εm=0 For u1 to be real u2−4△εm≥0 mu22≥2×△ε[△ε=10.2eV]. Thus (12mu2) min=2×10.2eV=20.4eV