The stone fell from a height of 20 meters. How long did the stone fall? How fast did it hit the ground?

V0 = 0 m / s.

g = 10 m / s2.

h = 20 m.

t -?

V -?

The height of the fall of the stone h is determined by the formula: h = V0 * t + g * t ^ 2/2. Since the stone begins to move from a state of rest V0 = 0 m / s, the formula will take the form: h = g * t ^ 2/2 …

g * t ^ 2 = 2 * h.

t = √ (2 * h / g).

t = √ (2 * 20 m / 10 m / s2) = 2 s.

The body’s acceleration g shows how the body’s speed changes over time: g = (V – V0) / t. The body moves with the acceleration of gravity g and without the initial velocity V0 = 0 m / s.

We will find the speed of the stone when hitting the ground by the formula: V = g * t.

V = 10 m / s2 * 2 s = 20 m / s.

Answer: the fall of the stone lasted t = 2 s, at the moment of impact on the ground it had a velocity of V = 20 m / s.