Q. A radioactive nucleus of mass number $A$, initially at rest, emits on $\alpha$-particle with a speed $v$. What will be the recoil speed of the daughter nucleus?
A) $\frac{2v}{(A - 4)}$
B) $\frac{2v}{(A + 4)}$
C) $\frac{4v}{(A - 4)}$
D) $\frac{4v}{(A + 4)}$
Explanation
(c) As per conservation law of momentum $0 = 4v + (A - 4)v_{r}$
$\therefore\ \ R$ecoil speed $v_{r} = \frac{4v}{(A - 4)}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.