v = initial velocity of launch of the stone = 12 m/s
θ = angle of the velocity from the horizontal = 30
Consider the motion of the stone along the vertical direction taking upward direction as positive and down direction as negative.
v₀ = initial velocity along vertical direction = v Sinθ = 12 Sin30 = 6 m/s
a = acceleration of the stone = - 9.8 m/s²
t = time of travel = 4.8 s
Y = vertical displacement of stone = vertical height of the cliff = ?
using the kinematics equation
Y = v₀ t + (0.5) a t²
inserting the values
Y = 6 (4.8) + (0.5) (- 9.8) (4.8)²
Y = - 84.1 m
hence the height of the cliff comes out to be 84.1 m
Here try this. The pic is the answer
Answer:

Explanation:
As we know that there is no external torque on the system of two disc
then the angular momentum of the system will remains conserved
So we will have

now we have

also we have

now from above equation we have

now we have


Before going to answer this question first we have to understand reflection and laws of reflection.
Reflection is the optical phenomenon in which light will bounce back to the same medium from which it had originated .
Whenever a light ray will incident on a mirror or any reflecting surface, it will be reflected. The ray which falls on the reflecting surface is called incident ray and the ray which is reflected is called reflected ray.
Let us consider a normal to the point of incidence.The angle made by incident ray with the normal is called angle of incidence.Let it be denoted as[ i ]
The angle made by the reflected ray with the normal is called angle of incidence.Let it be denoted as [r]
There are two types of reflection.One is called regular and other one is called as irregular.The laws of reflection is valid for both the types of reflection.
There are two laws of reflection.
FIRST LAW -It states that the incident ray,reflected ray and the normal to the point of incidence,all lie in one plane.
SECOND LAW- It states that that the angle of incidence is equal to the angle of reflection irrespective of the type of reflection.i.e i =r
Hence the correct answer will be angle of reflection.