The bomb is dropped , therefore its horizontal velocity = 600m/s and vertical velocity = 0
In 10 sec,
v = u + at
= u + gt
= 0 + 10x10
= 100 m/s
Horizontal velocity remains unchanged because there is no acceleration in the horizontal.
Therefore,
tan A = ( vertical velocity )/ (horizontal velocity )
= 100/600
= 1/6
Angle with the horizontal, A = tan-1 (1/6)