Answer :
The required height of the cliff is 4.4 m.
Given data:
The magnitude of initial speed of rock is, u = 12 m/s.
The time interval of hitting is, t = 2.0 s.
The given problem is clearly resolved using the concept and fundamentals of second kinematic equation of motion. As per the second kinematic equation of motion we have,
[tex]h =ut+\dfrac{1}{2}(-g)t^{2}[/tex]
Here,
h is the height of cliff.
g is the gravitational acceleration.
Solving as,
[tex]h =(12 \times 2)+\dfrac{1}{2}(-9.8) \times2^{2}\\\\h = 4.4\;\rm m[/tex]
Thus, we can conclude that the required height of the cliff is 4.4 m.
Learn more about the kinematic equations of motion here:
https://brainly.com/question/14355103