When studying a school course in physics, an important topic in the section of mechanics is the law of universal gravitation. In this article, we will take a closer look at what it is, and with what mathematical formula it is described, and also give examples of the force of gravity in everyday human life and on a cosmic scale.
Who Discovered the Law of Gravity
Before giving examples of the force of gravity, let's briefly describe who is credited with discovering it.
Since ancient times, people have observed the stars and planets and knew that they move along certain trajectories. In addition, any person who did not have special knowledge understood that no matter how far and high he threw a stone or other object, it always fell to the ground. But none of the people even guessed that the processes on Earth and celestial bodies are controlled by the same natural law.
In 1687, Sir Isaac Newton published a scientific work in which he first outlined the mathematicalformulation of the law of universal gravitation. Of course, Newton did not independently come to this formulation, which he personally recognized. He used some of the ideas of his contemporaries (for example, the existence of an inverse proportionality to the square of the distance of the force of attraction between bodies), as well as the accumulated experimental experience on the trajectories of the planets (Kepler's three laws). Newton's genius showed itself in the fact that after analyzing all the available experience, the scientist was able to formulate it in the form of a coherent and practically applicable theory.
Gravity Formula
The law of universal gravitation can be briefly formulated as follows: between all bodies in the Universe there is an attractive force, which is inversely proportional to the square of the distance between their centers of mass and directly proportional to the product of the masses of the bodies themselves. For two bodies with masses m1 and m2, which are at a distance r from each other, the studied law will be written as:
F=Gm1m2/r2.
Here G is the constant of gravity.
The force of attraction can be calculated using this formula in all cases, if the distances between the bodies are large enough compared to their sizes. Otherwise, and also in conditions of strong gravitation near massive space objects (neutron stars, black holes), one should use the theory of relativity developed by Einstein. The latter considers gravity as the result of a distortion of space-time. In Newton's classical lawgravity is the result of the interaction of bodies with some energy field, like an electric or magnetic field.
The Manifestation of Gravity: Examples from Everyday Life
Firstly, as such examples we can name any falling bodies from a certain height. For example, a leaf or the famous apple from a tree, a stone falling, raindrops, mountain landslides and landslides. In all these cases, the bodies tend to the center of our planet.
Secondly, when the teacher asks students to "give examples of gravity," they should also remember that all bodies have weight. When the phone is on the table or when a person is weighed on the scales, in these cases the body presses on the support. Body weight is a vivid example of the manifestation of the force of gravity, which, together with the reaction of the support, forms a pair of forces that balance each other.
If the formula from the previous paragraph is used for terrestrial conditions (substitute the mass of the planet and its radius into it), then the following expression can be obtained:
F=mg
It is it that is used in solving problems with gravity. Here g is the acceleration given to all bodies, regardless of their mass, in free fall. If there were no air resistance, then a heavy stone and a light feather would fall in the same time from the same height.
Gravity in the Universe
Everyone knows that the Earth, along with other planets, revolves around the Sun. In turn, the Sun, being inone of the arms of the spiral galaxy the Milky Way, rotates along with hundreds of millions of stars around its center. The galaxies themselves also approach each other in so-called local clusters. If we go back on a scale, then we should remember the satellites that revolve around their planets, the asteroids that fall on these planets or fly nearby. All of these cases can be remembered if the teacher asks students: "Give examples of the force of gravity."
Note that in recent decades the question of the main force on a cosmic scale has been called into question. In local space, it is undoubtedly the force of gravity. However, considering the issue at the level of the galaxy, another, as yet unknown force, associated with dark matter, comes into play. The latter manifests itself as anti-gravity.
