Question

$\beta$-particles ( Mass $m_e$) is emitted from the nucleus of mass number A with velocity u. Then, the recoil speed of the nucleus will be :

• A. $\frac{u{m}_e}{A-m_e}$
• B. $\frac{u{m}_e}{A+m_e}$
• C. $\frac{4u}{A-4}$
• D. $\frac{u}{A}$

Answer 1

Answer: (A)

$\frac{u{m}_e}{A-m_e}$

$u.m_e=(A-m_e)v^{\prime }$ or

$v^{\prime }=\frac{u{m}_e}{A-m_e}$