Question

A bomb of 12 kg explodes into two pieces of masses 4 kg and 8 kg. The velocity of 8kg mass is 6 m/sec. The kinetic energy of the other mass is

• A. 48 J
• B. 32 J
• C. 24 J
• D. 288 J

Answer 1

Answer: (D)

288 J

Answer 2

As the initial momentum of bomb was zero, therefore after explosion two parts should possess numerically equal momentum

i.e. $m _ { A } v _ { A } = m _ { B } v _ { B }$⇒ $4 \times v _ { A } = 8 \times 6$⇒ $v _ { A } = 12 \mathrm {~m} / \mathrm { s }$

∴ Kinetic energy of other mass A, = $\frac { 1 } { 2 } m _ { A } v _ { A } ^ { 2 }$

= $\frac { 1 } { 2 } \times 4 \times ( 12 ) ^ { 2 }$= 288 J.