Horizontal throw from 45 m at 20 m/s

A ball is thrown horizontally at 20 m/s from a height of 45 m (g = 10). Find the time of flight and the horizontal distance.

Step-by-step

1. t = √(2h/g) = √(2×45/10) = 3
   Free fall vertically: the time to land depends only on the height
2. x = v₀t = 20×3 = 60
   Uniform horizontal motion at constant velocity

Why it works

The vertical and horizontal motions are independent: vertically the ball is in free fall, so the height alone fixes the time, while horizontally it keeps its 20 m/s.

Common mistakes

• Letting the 20 m/s initial speed change the time of flight.
• Doubling the height because the path is a curve.

Related

projectile-motion vertical-throw projectile-320m-10ms