Question

Nucleus of mass number A, originally at rest, emits an α-particle with speed v. The daughter nucleus recoils with a speed

• A. $2v/(A + 4)$
• B. $4v/(A + 4)$
• C. $4v/(A - 4)$
• D. $2v/(A - 4)$

Answer 1

Answer: (C)

$4v/(A - 4)$

Answer 2

According to conservation of momentum $4v = (A - 4)v'$

⇒ $v' = \frac{4v}{A - 4}$.