Answer:
78.4m
Explanation:
In these situations, vertical and horizontal components need to be considered separately;
So, horizontal speed is irrelevant since we are talking about vertical height, i.e. the height of the cliff;
But, the fact that the speed is horizontal is relevant because this means the vertical speed initially is 0m/s;
The downwards movement of the ball is due to gravity, which is 9.8m/s²;
The time is given as 4.0s from the top of the cliff to the bottom;
We know the acceleration, time and initial speed so we can use this kinematic equation to solve for distance:
s = ut + ¹/₂at²
s = displacement (/distance)
u = initial vertical velocity = 0
t = time (time taken for the ball to fall) = 4
a = acceleration (downwards) = 9.8
Substitute these values into the equation to get the distance:
s = 0(4) + ¹/₂(9.8)(4)²
s = 78.4m
