A body thrown vertically upward from the surface of the earth reached a maximum height of 20m.

A body thrown vertically upward from the surface of the earth reached a maximum height of 20m. with what initial speed was the body thrown upward? neglect air resistance.

h = 20 m.

g = 9.8 m / s2.

V = 0 m / s.

V0 -?

When the body moves upward, only the gravity force m * g acts on it, directed in the opposite direction to the direction of motion, the body is braked to a complete stop with the acceleration of free fall g.

When braking a body, the acceleration of gravity is determined by the formula: g = (V0 ^ 2 – V ^ 2) / 2 * h.

Since the final speed of the body V = 0 m / s, it stopped, the formula will take the form: g = V0 ^ 2/2 * h.

V0 ^ 2 = 2 * h * g.

V0 = √ (2 * h * g).

V0 = √ (2 * 20 m * 9.8 m / s2) = 19.8 m / s.

Answer: the speed of the stone at the moment of throwing was V0 = 19.8 m / s.