Horizontal throw from 80 m at 15 m/s

A ball is thrown horizontally at 15 m/s from a height of 80 m (g = 10). Find the time of flight and the horizontal distance.

Step-by-step

1. t = √(2h/g) = √(2×80/10) = 4
   Free fall vertically: the time to land depends only on the height
2. x = v₀t = 15×4 = 60
   Uniform horizontal motion at constant velocity

Why it works

Vertically the ball is in free fall, so h = ½gt² gives the time from the height alone; horizontally the speed stays 15 m/s, so the range is that speed times the time.

Common mistakes

• Using the horizontal speed to find the time of flight.
• Multiplying the height by the speed instead of using x = v₀t.

Related

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