A rock is dropped from a cliff 80m above the ground. How long does it take to reach the ground ?

4.04 s

Explanation:

From the question given above, the following data were obtained:

Height (h) = 80 m

Acceleration due to gravity (g) = 9.8 m/s²

Time (t) =?

The time taken for the rock to get to the ground can be obtained as shown below:

h = ½gt²

80 = ½ × 9.8 × t²

80 = 4.9 × t²

Divide both side by 4.9

t² = 80/4.9

Take the square root of both side

t = √(80/4.9)

t = 4.04 s

Thus, it will take 4.04 s for the rock to get to the ground.