The stone is thrown upward at a speed of 20m / s to what maximum height it will rise, how long it will be in the air.

V0 = 20 m / s.

V = 0 m / s.

g = 10 m / s2.

hmax -?

t -?

The stone will move vertically upward with equal deceleration with the acceleration of gravity g until it comes to a complete stop. At the maximum height, its speed is V = 0 m / s.

The height of the rise h of the stone is determined by the formula: h = (V0 ^ 2 – V2) / 2 * g.

hmax = V0 ^ 2/2 * g.

hmax = (20 m / s) ^ 2/2 * 10 m / s2 = 20 m.

t = tp + tо, where tп is the time of ascent to the maximum height, tо is the time of lowering from the maximum height.

tп = to = (V0 – V) / g = V0 / g.

tp = 20 m / s / 10 m / s2 = 2 s.

t = 2 s + 2 s = 4 s.

Answer: the maximum height of raising the stone is hmax = 20 m, the flight time of the stone is t = 4 s.