Analysing the Question:
Neglecting air resistance
We are given:
mass (m) = 15 kg
time taken by the rock to reach the water (t) = 1 second
height of the cliff (h) = h m
initial velocity of the rock (u) = 0 m/s [ the rock was 'dropped' and not 'thrown' downwards]
acceleration of the rock due to gravity (a) = 9.8 m/s²
Finding the height to the cliff:
from the seconds equation of motion
s = ut + 1/2*at²
replacing the variables
h = (0)(1) + 1/2 * (9.8) *(1)²
h = 4.9 m
Therefore, the cliff is 4.9 m high
