A bomb of mass 16kg at rest, explodes into two pieces of masses 4kg and 12kg. After explosion, the velocity of the 12kg mass is 4m/s. What is the velocity of the 4kg piece?
-12 m/s
Using conservation of momentum we have initial total momentum equal to final total momentum.
0 = 4x + 12(4)
4x = -12
x = -12 m/s