During a military test, a 1200 kg missile is launched with an acceleration of 12 m/s² in a vertically positive direction. However, the test fails and the missile blasts 3.0 s after its launch into two pieces before reaching the destination. One of the broken pieces was thrice as large as the other. The heavier piece moved vertically up to a height of 1430 m. Determine the velocity of the lighter piece.