Question

A smooth ball 'A' moving with velocity 'V' collides with another smooth initial ball at rest. After collision both the balls move the same speed with angle between their velocities ${60}^0$. No external force acts on the systems of balls.
Choose the correct option(s).

• A. The speed of each ball after the collision is $\frac{V}{\sqrt{3}}$
• B. The speed of each ball after the collision is $\frac{2V}{\sqrt{3}}$
• C. The magnitude of change in momentum of ball B is $\left(\frac{mV}{\sqrt{3}}\right)$
• D. The magnitude of change in momentum of ball B is $\left(\frac{2mV}{\sqrt{3}}\right)$

Answer 1

The correct option is A The speed of each ball after the collision is $\frac{V}{\sqrt{3}}$

Let the mass of each ball is $=m$

Conversation is momentum along $\times$ axis, we get

$mV+m\times 0=(m+m)v^1\cos {30}^0$

$\Rightarrow$ $mV=2m{v}^1.\frac{\sqrt{3}}{2}\Rightarrow v^1=v/\sqrt{3}⟶\left(A\right)$