We have the equation of motion , [tex]s =ut+\frac{1}{2}at^2[/tex], where s is the displacement, u is the initial velocity, t is the time taken and a is the acceleration.
In this case s = ?
We have u = 8 m/s, t = 2.35 seconds and a = -9.81 [tex]m/s^2[/tex]
Substituting
[tex]s =8.00*2.35-\frac{1}{2}*9.81*2.35^2\\ \\ s = -8.29 m[/tex]
Here - ve sign means below the level of cliff it is 8.29 meter deep
So height of cliff = 8.29 meter
