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Q.
A bomb of mass $30\, kg$ at rest explodes into two pieces of masses $18\, kg$ and $12\, kg$. The velocity of $18\,kg$ mass is $ 6\,ms^{-1} $ . The kinetic energy of the other mass is
Momentum is conserved just before and after the explosion of the bomb. Initial momentum is zero, so the resultant momentum of the exploded pieces should be zero.
That is $m _{1} v _{1}= m _{2} v _{2}$
$
\Rightarrow(18)(6)=12\left( v _{2}\right)
$
$
\Rightarrow v _{2}=9 m / s
$
$\therefore$ the KE of $12 kg$ mass $=\frac{1}{2} 12\left(9^{2}\right)=486 J$