Use the first kinematic formula
Vf = Vi + at
10 = 0 + 1(t)
10 = t
10 seconds
Answer: n=4
Explanation:
We have the following expression for the volume flow rate
of a hypodermic needle:
(1)
Where the dimensions of each one is:
Volume flow rate 
Radius of the needle 
Length of the needle 
Pressures at opposite ends of the needle
and 
Viscosity of the liquid 
We need to find the value of
whicha has no dimensions, and in order to do this, we have to rewritte (1) with its dimensions:
(2)
We need the right side of the equation to be equal to the left side of the equation (in dimensions):
(3)
(4)
As we can see
must be 4 if we want the exponent to be 3:
(5)
Finally:
(6)
The acceleration due to gravity of the planet X is 1 m/s².
The given parameters;
- height above the ground, h = 100 m
- initial velocity of the rock, u = 15 m/s
- time of motion of the rock, t = 10 s
The acceleration due to gravity is calculated as follows;

Thus, the acceleration due to gravity of the planet X is 1 m/s²
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