A bomb of mass 30 kg initially at rest explodes into pieces 18 kg and 12 kg. The 18 kg piece moves at 6 m s⁻¹. Find kinetic energy of the 12 kg piece.
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A bomb of mass 30 kg initially at rest explodes into pieces 18 kg and 12 kg. The 18 kg piece moves at 6 m s⁻¹. Find kinetic energy of the 12 kg piece.

G1 Physics · Accepted Answer

Step 1 — Principle: During a very brief explosion, external impulse is negligible; total momentum is conserved. Step 2 — Working: Momentum conservation: 18×6=12|v₂|, hence |v₂|=9 m s⁻¹. Step 3 — Working: Its kinetic energy is ½×12×9²=486 J. Correct answer: B — 486 J.