IIT JEE , AIEEE Forum - Physics , Mechanics

joyfrancis

Let mass of the neutron be m ,

so mass of a nucleus having mass number A = m*A {neglecting protons}

Initial kinetic energy of the neutron = mv²/2

After conserving energy and momentum of the system we have

v' = v(1-A) / (1+A)---------(1)

(where v' is the final velocity of the neutron after the collision)

So, final kinetic energy of the electron is

Tf = mv'²/2

Tf = mv²/2*[(A-1)²/(A+1)²]--------(from 1)

Hence

Tf/Ti = (A-1)²/(A+1)²

(C)is correct