Answer:
It will take the boulder approximately 4.28 seconds to hit the road
Explanation:
The given height of the cliff from which the boulder falls, h = 90 feet
The equation that can be used to find the time it takes the boulder to fall is h = u·t + (1/2)·g·t²
Where;
h = The height of the cliff = 90 ft.
u = The initial velocity of the boulder = 0 m/s (The boulder is assumed to be at rest when it falls)
g - The acceleration due to gravity ≈ 9.81 m/s²
t = How long it will take for the boulder to hit the road below
Plugging in the values gives;
90 = 0 × t + (1/2)×9.81×t² = 4.905·t²
∴ t = √(90/4.905) ≈ 4.28
The time it takes the boulder to hit the road, t ≈ 4.28 seconds.