The body is thrown vertically upward at a speed of 20m / s. Determine the time and height of the body.

The body is thrown vertically upward at a speed of 20m / s. Determine the time and height of the body. Do not take into account air resistance.

V0 = 20 m / s.

g = 10 m / s2.

V = 0 m / s.

h -?

t -?

The maximum height h of the body can be found in two ways.

Method 1: according to the law of total mechanical energy.

At the initial moment of time the body has only kinetic energy Ek, and at the maximum height the body has only potential energy En: Ek = En.

m * V0 ^ 2/2 = m * g * h.

h = V0 ^ 2/2 * g.

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

Method 2: the body moves with the acceleration of gravity g.

The movement of the body h during uniformly accelerated motion is determined by the formula: h = (V0 ^ 2 – V ^ 2) / 2 * g.

Since the body has stopped at its maximum height, then V = 0 m / s.

h = V0 ^ 2/2 * g.

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

t = (V0 – V) / g.

t = V0 / g.

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

Answer: the time for lifting the body will be t = 2 s, the body will rise to a height of h = 20 m.