I believe because there is much less air and much more water in the bottom
To solve this problem we will use the given expression and derive it in order to find the algebraic expressions of velocity and position. These equations will be similar to those already known in the cinematic movement but will be subject to the previously given function. We start deriving the equation for velocity


Integrate acceleration equation



At 
Replacing,

Therefore the value of the first Constant is

The expression can be escribed as,

Calculate the velocity after 6s,



Now using the same expression we can derive the equation for distance




At t=0, x=0

Therefore the value of the second constant is


Calculate the distance traveled after 11 s
At 


Complete Question
The complete question is shown on the first uploaded image
Answer:
The value is 
Explanation:
From the question we are told that
The depth is 
The time taken for water to fall to below the river is 
The horizontal distance from the base of the vertical cliff is 
Generally the horizontal speed at the top is mathematically represented as

=> 
=> 
given that acceleration due to gravity is g = 10 m/s^2
speed of the rocket will reach to 0.9c

now by kinematics



Part b)
distance traveled by it in above time



so this is the distance covered by the object