A body of mass 4m at rest explodes into three fragments. Two pieces of mass m each move at equal speed v in perpendicular directions. The total kinetic energy generated is:
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A body of mass 4m at rest explodes into three fragments. Two pieces of mass m each move at equal speed v in perpendicular directions. The total kinetic energy generated is:

G1 Physics · Accepted Answer

Step 1 — Principle: During a very brief explosion, external impulse is negligible; total momentum is conserved. Step 2 — Working: Momentum of third piece (mass 2m) is −m v î−m v ĵ, giving speed v/√2. Step 3 — Working: KE=2(½mv²)+½(2m)(v²/2)=3mv²/2. Correct answer: B — 3mv²/2.