first find the block's velocity after the collision occurs.
1/2 (1.5 + 0.00225) V^2 = 1/2 (785)(0.0588)^2
so V = 1.344 m/s
using conservation of momentum we get:
(mv)bullet + 0 = (1.50225) (1.344)
0.00225 v = 2.02
v = 2.02 / 0.00225 = 897.3 m/s
Using distance = average velocity* time t = 0.0588 / (1.344/2) = 0.0875 s