Question

Two balls of mass $m$ and $2m$ are connected by a light inextensible string. The string is initially slack. The heavier ball is given velocity $v_0$ towards the right. Find impulse by the string on the ball of mass m when the string becomes tight.

Answer 1

By momentum conservation common velocity is v.

$\Rightarrow 2m{v}_o=3mv$

$\Rightarrow v=\frac{2}{3}{v}_0$

Momentum changed by block of mass $m=$ Impulse by string.

$\Rightarrow$ Impulse by string $=mv=\frac{2m}{3}{v}_0.$

Hence, solved.