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

Question

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Answer 1

As the initial momentum of bomb was zero, therefore after explosion two parts should possess numerically equal momentum
i.e. $m_{A} v_{A} = m_{B} v_{B} \Rightarrow 4 \times v_{A} = 8 \times 6 \Rightarrow v_{A} = 12 m / s$
$∴$ Kinetic energy of other mass $A, = \frac{1}{2} m_{A} v_{A}^{2}$
$= \frac{1}{2} \times 4 \times (12)^{2} = 288 J .$

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} \Rightarrow 4 \times v_{A} = 8 \times 6 \Rightarrow v_{A} = 12 m / 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 .