Question

A spacecraft of mass $M$ explodes into two parts when its velocity is $V$. After the explosion, one part of mass m is left stationary. What is the velocity of the other part?

• A. $\frac{MV}{(M+m)}$
• B. $\frac{MV}{(M-m)}$
• C. $\frac{mV}{(M-m)}$
• D. $\frac{MV}{m}$

Answer 1

The correct option is B

$\frac{MV}{(M-m)}$

Mass of the second part is $M-m$. If its velocity is $v$, then from conservation of linear momentum, we have
$MV=(M-m)v+m\times 0\Rightarrow v=\frac{MV}{(M-m)}$
Hence, the correct choice is (b).