The body is thrown from a certain height vertically upward with an initial speed of 30m / s.

The body is thrown from a certain height vertically upward with an initial speed of 30m / s. Find the speed in 10 seconds.

V0 = 30 m / s.

g = 9.8 m / s ^ 2.

t = 10 s.

V -?

When moving vertically upward, the body moves with the acceleration of gravity g, which is directed vertically downward, that is, against the speed of the body. Since the speed and acceleration are directed in opposite directions, the body is decelerated.

Let us find the lifting time of the body t1 until the body comes to a complete stop: g = V0 / t1.

t1 = V0 / g.

t1 = 30 m / s / 9.8 m / s ^ 2 = 3.06 s.

Let’s find the time of falling of the body t2 by the formula: t2 = t – t1.

t2 = 10 s – 3.06 s = 6.94 s.

The body time t2 = 6.94 s fell freely from a certain height with the acceleration of gravity g.

V = g * t2.

V = 9.8 m / s ^ 2 * 6.94 s = 68 m / s.

Answer: the body will have a speed V = 68 m / s.