## What is gravity?

Gravity (according to lat.** Gravitas**: **weight**), the force of mutual attraction between masses. According to Isaac Newton, gravity is an essential property of mass. According to Albert Einstein, gravity is a consequence of the curvature of space.

The gravitational field is the space in which the action of gravitational force is** felt**. It is characterized by special physical properties described by **two vectors** (gravitational force and gravitational field strength). Also two scalar quantities (gravitational potential and field energy).

## What is gravitational force?

Gravitational force is explained using Newton’s Law of Universal Gravitation. According to this rule, every heavy particle in the cosmos attracts every other massive particle with force proportional to the product of their masses and inversely proportional to the square of the distance between them. This broad physical law was formed through inductive findings.

Another, more contemporary method of stating the rule is: “Every point mass attracts every other point mass by force-directed down the line crossing both points.” The force is equal to the product of the two masses and inversely proportional to the square of the distance between the two-point masses.

## Gravitational force formula

Newton’s law of gravity is another name for the gravitational force formula. It also specifies the magnitude of the force that exists between two objects. Furthermore, the gravitational constant, G = 6.67, is included in the gravitational force formula.

F_1 = F_2 = G\frac{m_1 × m_2}{r^2}Furthermore, gravitational force attracts any two objects with the same mass. This gravitational force attracts because it always attempts to draw masses together rather than pushing them apart. Every item, including you, pulls every other object in the cosmos, known as Newton’s Universal Law of Gravitation.

## How to find the gravitational force

Gravity is a basic force in physics. An essential characteristic of gravity is universal: every item has a gravitational pull that attracts other objects. The gravitational force exerted on any item is proportional to the masses of both objects and the distance between them.

## The gravitational force between two objects

F_{grav}=\frac{G_{m1}G_{m2}}{d^2}This equation considers the masses of both objects and the distance between them to accurately compute the gravitational force on an item. You must use metric units for this particular equation. The masses of the items must be in kilograms (kg), and the distance must be in meters (m). Before proceeding with the computation, you must convert to these units. Smaller things can be weighed on a scale or balance to find out their weight in grams.

You’ll need to check up the approximate mass of larger things in a table or online. In most physics questions, you will be given the mass of the item. If you want to calculate the force of gravity between an item and the Earth, you must first know how distant the object is from the Earth’s centre. Once you’ve defined your equation’s variables, you may enter them in and solve them. Check that all of your units are metric and on the correct scale. The mass should be expressed in kilos and the distance in meters. Use the appropriate order of operations to solve the problem.

## The gravitational force of Earth

The gravity of Earth, represented by g, is the net acceleration imparted to objects due to the combined action of gravitation (from mass distribution inside Earth) and centrifugal force (from the rotation of the Earth). Gravitational acceleration at the Earth’s surface is roughly 9.81 m/s2, which implies that neglecting the effects of air resistance, the speed of an item falling freely will rise by approximately 9.81 metres per second squared.

The specific strength of Earth’s gravity fluctuates depending on where you are on the planet. The nominal “average” value at the Earth’s surface, known as standard gravity, is 9.80665 m/s2 by definition. Newton’s second rule of motion, or

*F = ma (force = mass * acceleration)*

states that the weight of an item on Earth’s surface is the downward force on that object.

## Gravitational force unit

In the International System of Units (SI), the unit of acceleration is m/s^{2}. However, the unit g (or g) is frequently used to distinguish acceleration relative to free-fall from basic acceleration (rate of change of velocity). One g is the force per unit mass due to gravity at the Earth’s surface (symbol: gn), defined as 9.80665 metres per second squared, or 9.80665 newtons of force per kilogram of mass. The definition of the unit does not change with location—the g-force experienced when standing on the Moon is nearly identical to that experienced on Earth.

## Einstein’s theory of gravitation

In the classical theory of gravitation, there are** absolute space** and **absolute time** as fundamental postulates. Einstein realized that the notion of absolute time, which is completely logical at first glance, is unsustainable. To compare the time between two observers in different reference systems, it is necessary to use some **signal.** The only physically possible way is to use a **light signal**. But as the speed of light is constant and independent of the observation system. Einstein showed that time must depend on the system. Time, and therefore the notion of the simultaneity of two events, is relative. In other words, gravity is only a** consequence** of the fact that the space-time continuum is not flat but curved.

## Newton’s laws

These are the three basic laws of classical physics that describe the connection between the motion of a body also the forces acting on the body. Newton’s laws apply only in classical **mechanics**, where the body’s speed is much lower than the speed of light, and the mass of the body is much higher than the mass of atomic parts **(electrons, protons, and neutrons). **

As well as that, in the case of extremely high velocities, comparable to the speed of light, or extremely small masses, comparable to the mass of atoms, other effects appear that are precisely describe by the laws of quantum mechanics and relativistic physics. Newton’s laws are:

**First law**(law of inertia)**Second law**(law of motion)**Third law**(law of action and reaction)

## The classical theory of gravity or Newton’s theory (law of gravity)

Newton linked Galileo’s laws of free fall with **Kepler’s** laws of planetary motion and derived a general law of mass attraction. The gravitational force with which a body of mass acts on a body is proportional to the diversity of masses and inversely proportional to the frame of their distance; it is an attractive force acting in the direction of the joint between the bodies.

In celestial mechanics, it is sufficient to assume that cosmic bodies are material points that interact with each other according to the size of their masses. However, as Newton has already done, it can prove that any spherical homogeneous mass. Or a mass composed of homogeneous concentric layers acts on any other body as well as the same force that would act; if its mass was concentrated in the center of the sphere.

## Who was Johannes Kepler?

**Johannes Kepler** (born December 27, 1571 – died November 15, 1630), German astronomer, mathematician, and astrologer. We know him for Kepler’s laws of** planetary motion**. Which he created in the scientific revolution of the 17th century, based on his works called; “Astronomer Nova”, “Harmonic Mundi”, and “Copernicus Astronomy Compendium”. In addition, these studies provided the basis for Isaac Newton’s theory of universal gravitational force.

## Kepler’s laws

1. The planets move i**n ellipses**, and the Sun is in one of the forces.

2.** Planets move so that the radius vector** (the vector that connects the center of the Sun and the center of the planets) describes equal surfaces at equal time intervals, regardless of the distance of the planets from the Sun (surface law).

3. **The squares of the time** of the orbits of the planets around the Sun are referred to as the cubes of the major semi-axes of their elliptical orbits

## Gravitational field

We say that the space around each body has special properties. Which we are closer to the body, the field is **stronger**. Also, as we move away, the field falls with the square distances. The strength of the gravitational field of a body of mass is the ratio of the gravitational force to the mass of the body on which that force acts. Also, the direction of the force determines the direction. The unit for gravitational field strength is** N / kg or m / s ^{2}**

^{ }(same as for acceleration).

The gravitational field is a vector field. The direction of the gravitational field is always according to the body that produced it. Also, if there are multiple material points, each of them will produce its own gravitational field in space. And the total gravitational field is the vector sum of the individual fields.

## Acceleration in the gravitational field

The Earth’s gravitational field is **radial**. Gravity is, in fact, the gravitational force by which the Earth attracts all bodies on or above the surface. According to Newton’s third law (Newton’s third law), each of these bodies **attracts** the Earth by force of equal amount and opposite orientation. Based on this, one might think that with the penetration towards the center of the Earth, the intensity of gravity (and thus the weight of the body) will increase.

However, the opposite is happening. If the body is at a greater depth in the Earth, the force of the Earth’s gravity (as well as the weight of the body) is less and less. This happens because he is attracted not only by the part of the Earth that is below him but also by the one above him. If the body were in the center of the Earth; it would be in a weightless state because then the same attractive forces would act on it. Thus, the Earth’s gravity is the largest on the Earth’s surface. The gravitational field of the Earth exists at any point, regardless of whether or not another body is at that point. The intensity of the gravitational field does not depend on how much mass is placed at a given point in the field.

## Interesting facts about gravity

The universe we can observe consists of about one **hundred billion galaxies**. Whose size can vary from dwarf galaxies with about 100,000 stars to giant galaxies with about 3,000 billion stars? On the other hand, Galaxies contain stars, planets, satellites, planetoids, comets, meteors, interstellar gas, dust, and black holes, all of which are held together by gravity.

**Gravitational force** is one of the basic forces in nature, also it is the one that keeps us on Earth. It is responsible for orbiting satellites around planets, planets around the Sun, the solar system around the center of our Milky Way galaxy, connecting galaxies into groups (clusters). The **length** connects opposite points, also the nearest and farthest point of the path (ellipse) of a body in motion around the central body. I.e. around the center of gravitational attraction, which passes through both forces, in astronomy, we call it the apse. In the case of the planetary paths, the apses are perihelion and aphelion, in the case of the Moon, the perigee, and apogee, also in the twin star paths, the periaster, and apoaster.

## Gravitational force example

Using one of the gravitational force checking devices, a lead ball was measured mass of **5 kg** and a ball of mass **10 g** at a distance of **7 cm** attract a force of **6.13 × 10 _{-10 }N**. What is the gravitational constant when we calculate it from these experimental data?

m1 = 5 kg

m2 = 10 g = 0,01 kg

r = 7 cm = 0,07 m

F = 6,13 × 10-10 N**G = ?**

Furthermore:

**F = G * m ^{1} * m_{2} / r^{2}**

G = F r

^{2}/ m

_{1}* m

_{2}

= 6,13 * 10

^{ -10}* 0,07

^{2}/ 5 * 0,01

=

**6 * 10**

^{-11}Nm^{2}/ kg^{2}## FAQ

**How to find the force of gravity?**

This rule may be summed up using the equation F = ma, where F is the force, m is the mass of the object, and a represents acceleration. Given this rule, we may compute the force of gravity of any object on the surface of the earth, using the known acceleration due to gravity.

**What type of force is gravity?**

Gravity or gravitational force is the force of attraction between any two objects in the cosmos. The force of attraction relies on the mass of the item and the square of the distance between them. It is by far the weakest known force in nature.

**What if there was no gravitational force?**

Humans and other items will become weightless without gravity. If we had no gravitational force, the atmosphere would escape into space, the moon would smash with the planet, the world would cease revolving, we would all feel weightless, the earth would collide with the sun, and as a consequence. We would all perish.