Thrown horizontally from 245 m at 25 m/s

A pebble is thrown horizontally at 25 m/s from a hilltop 245 m high (g = 10 m/s²). Find its time of flight and its horizontal distance.

Step-by-step

1. t = √(2h/g) = √(2×245/10) = 7
   Free fall vertically: the time to land depends only on the height
2. x = v₀t = 25×7 = 175
   Uniform horizontal motion at constant velocity

Why it works

The time of flight depends only on the vertical drop, not on the horizontal speed; the horizontal distance is the horizontal speed multiplied by that time.

Common mistakes

• Thinking a larger horizontal speed makes the pebble land sooner.
• Treating the 245 m height as the length of the slanted path.

Related

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