A bomb of mass 30 kg at rest explodes into two pieces of masses 18 kg and 12 kg. The velocity of 18 kg mass is `6 ms^(-1)`. The kinetic energy of the other mass is

Options

A. `324 J`
B. `486 J`
C. `256J`
D. `524 J`

Answer

D

Explanation

According to law of conservation of angular momentum,

`30 xx 0 = 18 xx 6 + 12 xx v implies 108 = -12 v implies v = -9 m//s`
Negative sign indicates that both fragments move in opposite direction:
`K.E.` of `12 kg = 1/2 mv^2 = 1/2 xx 12 xx 81 = 486 J`