Question

A rock is dropped off a cliff that is 138 m tall. How long will it take to hit the ground? What is the rock’s final velocity?

Answer 1

y = (1/2).g,t² + v₀.t, where:
y = distance = 138 m
g = 9.8 m/s² (gravity)
v₀ = initial speed = 0

138 = (1/2)(9.8).t² + 0 →138= 4.9.t² and t² = 138/4.9 = 28.16 and t = 5.3 s

Final speed V(final) = V(initial) + gt

V(final) = 0 + 9.8(5.3) = 51.94 m/s ≈ 52 m/s