Explanation
Using momentum conservation on bullet + gun as a system
⇒ initial momentum= Final momentum
0=−MV+mv
⇒mv=MV..........(1)
Now total energy =E
⇒12MV2+12mv2=E
From (1)
V=mvM
⇒12Mm2M2v2+12mv2=E
12mv2(mM+1)=E
12mv2=EMM+m
↓
K.E bullet
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