Question

A bomb of mass 16 kg at rest explodes into two pieces of masses 4 kg and 12 kg. The velocity of the 12 kg mass is 4 $ms^{-1}.$The kinetic energy of the other mass is:

• A. 144J
• B. 288J
• C. 192J
• D. 96J

Answer 1

Answer: (B)

288J

Answer 2

Here momentum of the system is remaining conserved as no external force is acting on the bomb (system). Initial momentum (before explosion) = Final momentum (after explosion) Let velocity of 4 kg mass is v m/s. From momentum conservation we can say that its direction is opposite to velocity of 12 kg mass. $from \, \quad\vec{P}_{i}=\vec{P}_{f}$ $\Rightarrow 0=12\times4-4\times v \Rightarrow v=12 m/ s$ KE of 4 kg mass =$\frac{4\times\left(12\right)^{2}}{2} =288 J$