The gravitational acceleration at any distance r is given by

where G is the gravitational constant, M the Earth's mass and r is the distance measured from the center of the Earth.
The Earth's radius is
, so the meteoroid is located at a distance of:

And by substituting this value into the previous formula, we can find the value of g at that altitude:

Answer:
d = 421.83 m
Explanation:
It is given that,
Height, h = 396.9 m
Horizontal speed, v = 46.87 m/s
We need to find the distance traveled by the ball horizontally. Let t is the time taken by the ball. Using second equation of motion for vertical direction. So,

Now d is the distance covered by the cannonball. So,

Hence, this is the required solution.