Thrown horizontally from 180 m at 20 m/s

A stone is thrown horizontally at 20 m/s from the top of a 180 m cliff (g = 10 m/s²). Find the time it takes to reach the bottom and the horizontal distance it covers.

Step-by-step

1. t = √(2h/g) = √(2×180/10) = 6
   Free fall vertically: the time to land depends only on the height
2. x = v₀t = 20×6 = 120
   Uniform horizontal motion at constant velocity

Why it works

Vertically the stone is in free fall, so the 180 m height fixes the falling time; horizontally no force acts, so it keeps 20 m/s, and both directions share the same time.

Common mistakes

• Dividing the cliff height by the 20 m/s horizontal speed to get the falling time.
• Doubling the time because the path is a curve.

Related

projectile-motion echo-well projectile-125m-30ms