# From a height of 15 m above the ground, a ball was thrown vertically downward, which fell to the ground in 1 s.

July 28, 2021 | education

| **From a height of 15 m above the ground, a ball was thrown vertically downward, which fell to the ground in 1 s. At what height from the ground was the ball 0.5 s after the start of the flight?**

Data: h0 (starting height) = 15 m; t (duration of the fall) = 1 s; t1 (considered time) = 0.5 s.

Constants: g (acceleration due to gravity) ≈ 10 m / s2.

1) Ball throw speed: S = h0 = V0 * t + a * t ^ 2/2 = V0 * t + g * t ^ 2/2 and V0 = (h0 – g * t ^ 2/2) / t = (15 – 10 * 1 ^ 2/2) / 1 = 10 m / s.

2) Height after 0.5 s fall: h = h0 – h1 = h0 – V0 * t1 – g * t1 ^ 2/2 = 15 – 10 * 0.5 – 10 * 0.5 ^ 2/2 = 15 – 5 – 1.25 = 8.75 m.

Answer: After 0.5 s of flight, the ball was at a height of 8.75 m.

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