Question

A neutron moving with velocity u collides with a stationary $\alpha -particle$ The velocity of the neutron after collision is

• A. $-\frac{3\cup }{5}$
• B. $\frac{3\cup }{5}$
• C. $\frac{2\cup }{5}$
• D. $-\frac{2\cup }{5}$

Answer 1

The correct option is A $-\frac{3\cup }{5}$

Mass of alpha particle is $4$ times to neutron

according to the condition alpha paticle is at rest so its velocity is zero

now the final velocity of neutron is calculated from this formula

$U^{\prime }=(m-1-m_2÷m_1+m_2)U^1$

by putting$,$

$U^{\prime }=(1-4÷1+4)$

$=-3U/5$

Negative sign shows reverse direction of neutro$.$

Hence,

option $\left(A\right)$ is correct answer.