As the first part comes to the rest means, then it will fall under gravity directly.
First of all maximum height,
H=
g
u²sin²θ
H=
2×10
400×(
2
1
)
H=10m.
As initially the full projectile was supposed to land at A but due to explosion first part land at A', so to make the centre of mass lies at A the second part should lie at B.
