Mention of the concept of acceleration of free fall is often accompanied by examples and experiments from school books, in which various objects of different weight (in particular, a pen and a coin) were dropped from the same height. It seems absolutely obvious that objects will fall to the ground at different intervals (the pen may not fall at all). Consequently, the free fall of bodies does not obey only one specific rule. However, this seems to be taken for granted only now, some time ago it was necessary to conduct experiments in order to confirm this. Researchers reasonably suggested that a certain force acts on the fall of bodies, which affects their movement and, as a result, the speed of vertical movement. This was followed by no less famous experiments with glass tubes with a coin and a pen inside (for the purity of the experiment). Air was pumped out of the tubes, after which they were hermetically sealed. Imagine the surprise of the researchers, when both the pen and the coin, despite obviously different weights, fall at the same rate.
Such experience served as the basis not only for the creation of the concept of free fall acceleration (USP), but also for the assumption that free fall (that is, the fall of a body that is not affected by any opposing forces) is possible only in a vacuum. In the air, which is a source of resistance, all bodies move with acceleration.
So the concept of gravity acceleration appeared, which received the following definition:
- the fall of bodies from a state of rest under the influence of the Earth's gravity .
The letter of the Greek alphabet g (je) was assigned to this concept.
On the basis of such experiments, it became clear that USP is absolutely characteristic of the Earth, since it is known that there is a force on our planet that attracts all bodies to its surface. However, another question arose: how to measure this quantity and what it equals.
The solution to the first question was found quite quickly: scientists using special photography recorded the position of the body during a fall in airless space at different times. It turned out a curious thing: all the bodies in a given place on Earth fall with the same acceleration, which, however, varies somewhat depending on the specific location on the planet. At the same time, the height from which the bodies began to move 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 average man) is explained both by the shape of the Earth (which is not quite 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 it is rounded to 10 N / kg.
g = 9.8 N / kg
Against the background of the data obtained, it is clear that the acceleration of gravity on other planets differs from that on Earth. Scientists came to the conclusion that it can be expressed by the following formula:
g = G x M planets / (R planets) (2)
In simple words: G (gravitational constant (6.67 • 10 (-11) m2 / s2 ∙ kg)) must be multiplied by M - the mass of the planet -, divided by R - the radius of the planet squared. 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. As you can see, the accelerations on two planets are very different from each other. In particular, on Earth it is almost 6 times larger! Simply put, the Moon attracts objects located on its surface with a force less than 6 times less than the Earth. That is why the astronauts on the moon, whom we see on television, seem to be getting lighter. In fact, they lose weight (not mass!). The result is fun effects like jumping a few meters, a sense of flying and long steps.