Question

A ball is thrown horizontally at 20 m/s from the top of a cliff 50 meters high. how far from the base of the cliff does the ball strike the ground?

Answer 1

You need to divide the motion into its component: vertical and horizontal motion.

The time taken to fall vertically from the cliff is equal to the time taken to move horizontally.

Using the vertical component, which is an accelerated motion with an initial velocity equal to zero, we can solve for t:
h = 1/2 · g · t²

t = √(2·h / g)
  = √(2·50 / 9.8)
  = 3.2 s

Horizontally, it is a constant motion:
d = v · t
   = 20 · 3.2
   = 64 m

The ball will strike the ground at a distance of 64 meters from the cliff.