Horizontal throw from 125 m at 30 m/s

A ball is thrown horizontally at 30 m/s from a height of 125 m (g = 10). Find the time of flight and the horizontal distance.

Step-by-step

1. t = √(2h/g) = √(2×125/10) = 5
   Free fall vertically: the time to land depends only on the height
2. x = v₀t = 30×5 = 150
   Uniform horizontal motion at constant velocity

Why it works

Free fall downwards fixes the time from the height, and the horizontal motion is uniform, so the range is simply the horizontal speed multiplied by that time.

Common mistakes

• Taking the time as the height divided by the horizontal speed.
• Forgetting that the horizontal speed stays constant all the way down.

Related

projectile-motion vertical-throw n-phy-projectile-1