How long does it take for a ball freely falling from a height of 30 meters to travel 20 meters? What is its speed when it falls?

Given: H (initial height of a given ball) = 30 m; S (path required for the ball to travel) = 20 m; free fall.

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

1) The time during which the given ball passed 20 m: S = g * t2 / 2, whence t = √ (2 * S / g) = √ (2 * 20) / 10) = 2 s.

2) The speed of a given ball at the moment of falling: H = V2 / 2g, whence V = √ (2 * g * H) = √ (2 * 10 * 30) = 24.5 m / s.

Answer: The given ball is passed 20 m in 2 s; its speed at the moment of falling will be equal to 24.5 m / s.