Answer:

Explanation:
The motion of a projectile consists of two independent motions:
- A uniform motion along the horizontal direction (constant velocity)
- A uniformly accelerated motion along the vertical direction (constant acceleration)
The time of flight of a projectile is given by

where
is the initial vertical velocity
is the acceleration due to gravity
Here the time of flight is
t = 8 s
So, the initial vertical velocity is:

At the same time, the horizontal distance covered by the projectile is given by

where
is the horizontal velocity, which is constant
t is the time of flight
Here we know that the range of the projectile is 0.3 km, so
d = 0.3 km = 300 m
So the horizontal velocity is

Therefore, we can find the angle of projection of the projectile by using:
