# The body is thrown from the surface of the earth vertically upwards at a speed of 9 m / s.

The body is thrown from the surface of the earth vertically upwards at a speed of 9 m / s. Body speed decreased 3 times at altitude …

V0 = 9 m / s.

V = V0 / 3.

g = 9.8 m / s ^ 2.

h -?

The body, which is moving, is acted upon by the force of gravity; therefore, the body moves with the acceleration of gravity g, which is directed in the opposite direction of the initial velocity V0.

We express the height of the body h by the formula: h = (V0 ^ 2 – V ^ 2) / 2 * g, where V0 is the initial speed of movement, V is the final speed of the body, g is the acceleration of gravity.

h = (V0 ^ 2 – V0 ^ 2/9) / 2 * g = 4 * V0 ^ 2/9 * g.

h = 4 * (9 m / s) ^ 2/9 * 9.8 m / s ^ 2 = 3.6 m.

Answer: at a height of h = 3.6 m, the speed of the body will decrease by 3 times.

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