Question

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

Answer 1

Given ;
m1 = 8kg , m2 = 4kg
v of 12 kg = 0
v of 8 kg = 6 m/s
v of 4 kg = v

Vcm = (m1v1+m2v2)/(m1+m2)

0 = [(8×6)+(4×v)] ÷ (8+4)
48 + 4v = 0
4v = -48
v = -12 m/s

K.E = (1/2)mv^2
= (1/2)×4×(-12×-12)
= 2×(144)
= 288 J
________________
Hence the kinetic energy of 4kg will be 288 J