A stone was thrown from a 20m high tower with zero initial velocity. neglecting the air resistance

A stone was thrown from a 20m high tower with zero initial velocity. neglecting the air resistance, determine how long the stone falls. how fast will it fly up to Earth?

The fall of a stone can be considered as a uniformly accelerated rectilinear movement. The acceleration due to gravity is 9.8 m / s2. Let us express the time of the fall of the stone from the formula for moving the body with constant acceleration at zero initial velocity:

S = at ^ 2/2;

t = √ (2S / a) = √ (2 * 20 / 9.8) = 2.02 s;

Let’s find the final speed of the stone:

v = v0 + at = 0 + 9.8 * 2.02 = 19.8 m / s.

Answer: t = 2.02 s; v = 19.8 m / s.