John throws a rock down with speed 14 m/s from the top of a 30-m tower.If g = 9.8 m/s² and air resistance is negligible,what is the rock's speed just as it hits the ground? A)12 m/s B)28 m/s C)350 m/s D)784 m/s

Question

Quizplus · Accepted Answer

Using the formula vf^2 = vi^2 + 2ad, we can find the final velocity of the rock just as it hits the ground.

vi = 14 m/s (initial velocity)
a = 9.8 m/s^2 (acceleration due to gravity)
d = 30 m (height of tower)

vf^2 = (14 m/s)^2 + 2(9.8 m/s^2)(30 m)
vf^2 = 196 + 588
vf^2 = 784
vf = sqrt(784) = 28 m/s

Therefore, the rock's speed just as it hits the ground is 28 m/s, which corresponds to choice B.

John Throws a Rock Down with Speed 14 M/s from the Top