Question

A person kicks a rock off a cliff horizontally with a speed of 20.0 m/s. It takes 7.0 seconds to hit the ground, find:
a. height of the cliff
b. final vertical velocity
c. horizontal range

Answer 1

This problem involved half projectile.
initial velocity, vo = 20 m/s
time of flight, t = 7 s

(a) Simply use the formula to get the height, h:

h = vo*t - (1/2)gt^2

(b) To get the final vertical velocity or terminal velocity (vf), use the formula:

(vf)^2 - (vo)^2 = 2gh

(c) Use the formula find the horizontal distance traveled, R:
R = vo * cos(θ) * t
But since the angle involved with respect to horizontal is zero, and cos(0) = 1, we have

R = vo * t

Hope this helps~ `u`

Answer 2

But what's g?