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

Options

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

Answer

B

Explanation

According to law of conservation of angular momentum,

`30 xx 0 = 18 xx 6 + 12 xx v rArr 108 = -12v rArr v = -9m//s`
Negative sign in 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