A stone is thrown vertically upward at a speed of V0 = 20 m / s. Determine the time of the rise of the stone.

V0 = 20 m / s.

V = 0 m / s.

g = 10 m / s2.

t -?

Since only gravity acts on the stone, it will move uniformly with the acceleration of gravity g. First, it will slow down to a complete stop, and then, it will begin its downward movement. During the ascent time t the speed of the stone will decrease from V0 = 20 m / s to V = 0 m / s.

Let us write down the definition for the acceleration of gravity g: g = (V0 – V) / t = V0 / t.

t = V0 / g.

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

Answer: the time for lifting the stone is t = 2 s.