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?

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