When studying the school course of physics, the Law of universal gravitation is an important topic in the section of mechanics. In this article, we will examine in more detail what it is and with what mathematical formula it is described, as well as give examples of gravity in everyday life and on a cosmic scale.
Who discovered the law of gravity
Before giving examples of the force of universal gravitation, we will briefly tell to whom they attribute its discovery.
Since ancient times, people have watched stars and planets and knew that they are moving 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, he always fell to the ground. But not one of the people even guessed that the same natural law controls the processes on Earth and celestial bodies.
In 1687, Sir Isaac Newton published a scientific work in which he first set out the mathematical formulation of the Law of universal gravitation. Of course, Newton did not independently come to this formulation, which he personally recognized. He used some ideas of his contemporaries (for example, the existence of inverse proportionality from the square of the distance of the attractive force between bodies), as well as accumulated experimental experience on the trajectories of planetary motion (three Kepler laws). The genius of Newton proved himself in that by analyzing all the available experience, the scientist was able to formalize it in the form of a harmonious and practically suitable 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 that is inversely proportional to the square of the distance between their centers of mass and directly proportional to the product of the masses of bodies themselves. For two bodies with masses m 1 and m 2 , which are at a distance r from each other, the studied law is written in the form:
F = G * m 1 * m 2 / r 2 .
Here, the value of G is the constant of gravity.
The force of attraction can be calculated by this formula in all cases if the distances between the bodies are large enough compared to their size. Otherwise, as well as in conditions of strong gravity near massive space objects (neutron stars, black holes), the theory of relativity developed by Einstein should be used. The latter considers gravity as a result of the distortion of space-time. In the classical law of Newton, gravity is the result of the interaction of bodies with a certain energy field, like an electric or magnetic field.
Manifestation of gravity: examples from everyday life
Firstly, as such examples we can name any fall of bodies from a certain height. For example, a leaf or a famous apple from a tree, a fall of stone, raindrops, the phenomenon of mountain landslides and landslides. In all these cases, bodies tend to the center of our planet.
Secondly, when the teacher asks students: “Give examples of gravity,” they should also remember the existence of weight in all bodies. 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 striking example of the manifestation of gravity, which, together with the reaction of the support, forms a pair of balancing forces.
If you use the formula from the previous paragraph for terrestrial conditions (substitute the mass of the planet and its radius), then you can get the following expression:
F = m * g
It is used in solving problems with gravity. Here g is the acceleration reported to all bodies, regardless of their mass during free fall. If there were no air resistance, the heavy stone and light feather would fall from the same height in the same time.
Gravity in the universe
Everyone knows that the Earth, along with other planets, revolves around the Sun. In turn, the Sun, being in one of the arms of the spiral galaxy the Milky Way, rotates with hundreds of millions of stars around its center. The galaxies themselves also approach each other in the so-called local clusters. If you go back on a scale, then you should remember the satellites that revolve around their planets, the asteroids that fall on these planets or fly nearby. All these cases can be remembered if the teacher asks the students: "Give examples of gravity."
Note that in recent decades, the issue of the main force on a cosmic scale has been called into question. In local space, it is without a doubt the force of gravity. However, when considering the issue at the galactic level, another, as yet unknown, force associated with dark matter comes into play. The latter manifests itself in the form of antigravity.