Acceleration of gravity

The mention of the concept of acceleration of free fall is often accompanied by examples and experiments from school textbooks, in which various objects (in particular, a pen and a coin) were dropped from the same height. It seems absolutely obvious that the objects will fall to the ground at different intervals (the pen can not fall at all). Therefore, the free fall of bodies does not obey only one particular rule. However, this seems self-evident only now, some time ago it was required to conduct experiments in order to confirm this. Researchers reasonably assumed that a certain force acts on the fall of bodies, which affects their movement and, as a consequence, the speed of vertical movement. Then followed no less famous experiments with glass tubes with coins and a pen inside (for the purity of the experiment). Air was pumped out of the tubes, after which they were sealed. What was the surprise of the researchers, when both the pen and the coin, despite apparently different weight, fall at the same speed.

This experience served as the basis not only for the creation of the concept of acceleration of free fall (USP), but also for the assumption that a free fall (that is, a fall of a body that no opposing forces act) is possible only in a vacuum. In the air, which is the source of resistance, all bodies move with acceleration.

So the notion of the acceleration of free fall , which received the following definition:

• The fall of bodies from a state of rest under the influence of the force of gravity of the Earth.

This concept was assigned the letter of the Greek alphabet g (xe).

On the basis of such experiments, it became clear that the USP is absolutely accurate for the Earth, since it is known that on our planet there is a force that draws to its surface all the bodies. However, another question arose: how to measure this value and what it equals.

The solution of the first question was found quite quickly: the scientists, using special photography, fixed the position of the body during a fall in the airless space at different intervals of time. It turned out a curious thing: all the bodies in the given place of the Earth fall with the same acceleration, which, however, differs somewhat depending on the specific place on the planet. At the same time, the height from which the bodies started their movement does not matter: it can be 10, 100 or 200 meters.

It was possible to find out: the acceleration of gravity on Earth is approximately 9.8 N / kg. In fact, this value can be in the range from 9.78 N / kg to 9.83 N / kg. This difference (albeit small in the eyes of the layman) is explained by the shape of the Earth (which is not exactly spherical, but flattened at the poles), and by the daily rotation of the Earth around the Sun. As a rule, an average value of 9.8 N / kg is taken for calculations, with large numbers rounded to 10 N / kg.

G = 9.8 N / kg

Against the background of the data obtained, it can be seen that the acceleration of gravity on other planets differs from that on the Earth. Scientists came to the conclusion that it can be expressed by the following formula:

G = G × M of the planet / (R of the planet) (2)

In simple words: G (the gravitational constant (6.67 × 10 (-11) m2 / s2 ∙ kg)) must be multiplied by M - the planet's mass, divided by R - the radius of the planet in the square. For example, we find the acceleration of gravity on the Moon. Knowing that its mass is 7.3477 · 10 (22) kg, and the radius is 1737.10 km, we find that USP = 1.62 N / kg. Apparently, the accelerations on the two planets are strikingly different from each other. In particular, on the Earth it is almost 6 times larger! Simply put, the Moon attracts objects located on its surface, with a force less than 6 times that of Earth. That is why the astronauts on the Moon, whom we see on television, seem to become easier. In fact, they lose weight (not weight!). The result is funny effects like jumping a few meters, a sense of flying and long steps.