Question

A bomb of mass 30 kg at rest explodes into two pieces of masses 18 kg and 12 kg. The velocity of 18kg mass is $6{ms}^{-1}$. The KE of the other mass is

• A. 256 J
• B. 486 J
• C. 524 J
• D. 324 J

Answer 1

Answer: (B)

486 J

Here, $m_1=18kg,m_2=12kg,v_2=6{ms}^{-1}$
In accordance with conservation law of momentum
$v_2=\frac{m_1{v}_1}{m_2}=\frac{18\times 16}{12}=9m/s$
$\therefore$ KE of 12 kg mass piece
$K_2=\frac{1}{2}{m}_2{v}_2^2=\frac{1}{2}\times 12\times {\left(9\right)}^2=486J$