It is known that the planet Earth attracts any body to its core with the help of the so-called gravitational field . This means that the greater the distance between the body and the surface of our planet, the more the Earth acts on it, and the more pronounced the force of gravity.
A body falling vertically downward is still affected by the aforementioned force, due to which the body will certainly fall down. The question remains: what will be its speed in the fall? On the one hand, the object is influenced by air resistance, which is strong enough, on the other hand, the body is more strongly attracted to the Earth, the farther it is from it. The first - it will obviously be an obstacle and reduce the speed, the second - give acceleration and increase speed. Thus, another question arises as to whether it is precisely free fall that is possible under terrestrial conditions. Strictly speaking, a free fall of a body is possible only in a vacuum, where there are no interferences in the form of resistance to air flow. However, in the framework of modern physics, the free fall of the body is considered to be a vertical movement that does not encounter interference (air resistance can be neglected).
The thing is that to create conditions where other forces, in particular, the same air, can not act on the falling object, can only be artificially. It was experimentally proved that the free fall rate of a body in a vacuum is always equal to the same number, regardless of body weight. This movement was called uniformly accelerated. It was first described by the famous physicist and astronomer Galileo Galilei more than 4 centuries ago. The relevance of such conclusions has not lost its strength to this day.
As already mentioned, the free fall of the body in the framework of everyday life is a conditional and not entirely correct name. In fact, the free fall rate of any body is uneven. The body moves with acceleration, due to which such a movement is described as a special case of uniformly accelerated motion. In other words, every second the speed of the body will change. With this reservation in mind, you can find the free fall rate of the body. If we do not give the subject acceleration (that is, we don’t throw it, but simply lower it from a height), then its initial velocity will be zero: Vo = 0. Every second, the speed will increase in proportion to the elapsed time and acceleration: gt.
It is important to comment on the input of the variable g. This is the acceleration of gravity. Earlier, we already noted the presence of acceleration when the body falls under normal conditions, i.e. in the presence of air and when exposed to gravity. Any body falls to the Earth with an acceleration equal to 9.8 m / s2, regardless of its mass.
Now, bearing in mind this reservation, we derive a formula that will help calculate the free fall rate of the body:
V = Vo + gt.
That is, to the initial speed (if we gave it to the body by throwing, pushing or other manipulations) we add the product of the acceleration of gravity by the number of seconds that it took the body to reach the surface. If the initial velocity is zero, then the formula takes the form:
V = gt.
That is, simply the product of the acceleration of free fall on time.
Similarly, knowing the speed of free fall of an object, you can derive the time of its movement or initial speed.
You should also distinguish the formula for calculating the speed of a body thrown at an angle to the horizon, since in this case forces will act that gradually slow down the speed of the thrown object.
In the case considered by us, only the force of gravity and the resistance of air flows act on the body, which, by and large, does not affect the change in speed.