A 12 kg bomb at rest explodes into two pieces of 4 kg and 8 kg . If the momentum of 4 kg piece is 20 Ns , the kinetic energy of the 8 kg piece is

Question

A 12 kg bomb at rest explodes into two pieces of 4 kg and 8 kg . If the momentum of 4 kg piece is 20 Ns , the kinetic energy of the 8 kg piece is, 25 J, 20 J, 50 J, 40 J

MARKS App · Accepted Answer

The explosion is due to internal forces so the momentum of the system is conserved. Applying conservation of momentum, 0 = m 1 v + m 2 v ′ 0 = 20 + 8 v ′ v ′ = - 20 8 = - 5 2 m s - 1 After the explosion, Then, K E = 1 2 m v ′ 2 = 1 2 × 8 × 5 2 2 = 1 2 × 8 × 25 4 = 25 J

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