The force of gravity is the value for which the body is attracted to the ground under the action of its attraction. This indicator directly depends on the weight of a person or mass of the subject. The more weight, the higher. In this article we will tell you how to find gravity.
From the school year of physics: the strength of attraction is directly proportional to the weight of the body. It is possible to calculate the value according to the formula F \u003d M * G, where G is a coefficient equal to 9.8 m / s 2. Accordingly, for a person who weighs 100 kg, the strength of attraction is 980. It is worth noting that in practice everything is a little different, and for the power of gravity is influenced by many factors.Factors affecting gravity:
- distance from the ground;
- geographical location of the body;
- times of Day.
If the body is not in the horizontal direction, then it is worthwhile to take into account the angle to which the object from the horizon is rejected. As a result, the formula will have the following form: F \u003d M * G - FLATES * SIN. The force of gravity in Newton is measured. For calculations, use the speed measured in m / s. To do this, share the speed as km / h by 3.6.
Definition 1.
The force of gravity is considered an application to the center of gravity of the body, determined by hanging the body on the thread for its different points. At the same time, the intersection point of all directions that are marked by the thread, and will be considered the center of gravity of the body.
The concept of gravity
The strength of gravity in physics is considered the force acting on any physical body, which is near the earth's surface or another astronomical body. The force of gravity on the surface of the planet, by definition, will be folded from the gravitational attraction of the planet, as well as the centrifugal force of inertia, provoked by the daily rotation of the planet.
Other forces (for example, the attraction of the Sun and the Moon) due to their smallness are not taken into account or are studied separately in the format of temporary changes in the gravitational field of the Earth. Gravity informs all bodies, regardless of their mass, equal to acceleration, presenting conservative power. It is calculated on the basis of the formula:
$ \\ vec (p) \u003d m \\ vec (g) $
where $ \\ vec (G) $ is an acceleration, which is communicated to the body of gravity, designated as an acceleration of free fall.
On the bodies, moving relative to the surface of the Earth, in addition to gravity, also has a direct impact of a Coriolis force, which represents the force used when studying the motion of the material point in relation to the rotating reference system. The attachment of the Coriolis force to the physical force acting on the material point will take into account the effect of rotation of the reference system to such a movement.
Important formulas for calculating
Accordingly, the law of global gravity, the strength of the gravitational attraction, affecting the material point with its mass of $ m $ on the surface of an astronomical spherically symmetric body with a mass of $ M $, will be determined by the ratio:
$ F \u003d (g) \\ FRAC (Mm) (R ^ 2) $, where:
- $ G $ -gavitational constant,
- $ R $ - Body Radius.
The specified ratio is fair, if we assume the spherically symmetric mass distribution by body volume. Then the power of gravitational attraction is sent directly to the center of the body.
The module of the centrifugal force of the inertia is $ q $ acting on the material particle is expressed by the formula:
$ Q \u003d MAW ^ $ 2, where:
- $ a $ - the distance between the particle and the axis of rotation of the astronomical body, which is considered
- $ W $-ingl speed of its rotation. At the same time, the centrifugal force of inertia becomes perpendicular to the axis of rotation and directed away from it.
In vector format, the expression for centrifugal force inertia is written as follows:
$ \\ vec (q) \u003d (mw ^ 2 \\ VEC (R_0)) $, where:
$ \\ vec (R_0) $ - vector, perpendicular axis of rotation, which is carried out from it to the specified material point, staying near the ground surface.
At the same time, the gravity of $ \\ vec (P) $ will be equivalent to the amount of $ \\ vec (f) $ and $ \\ vec (q) $:
$ \\ vec (p) \u003d \\ vec (f) \u003d \\ VEC (q) $
Law of attraction
Without the presence of gravity, it would be impossible to be the origin of many, now we have been natural, things: so, there would be no convergence from the mountains of avalante, the flow of rivers, rains. The Earth's atmosphere can be maintained solely due to the effects of gravity. Planets with a smaller mass, for example, a moon or mercury, lost their entire atmosphere with a rather rapid pace and became defenseless in front of the streams of aggressive outer radiation.
The atmosphere of the Earth played crucial importance in the process of forming life on Earth, it. In addition to the strength of gravity, the force of attraction of the moon is also affected on Earth. Due to its close neighborhood (in a space scale), the existence of sings and tides is possible on Earth, and many biological rhythms are coinciding with the lunar calendar. The force of gravity, therefore, should be considered in the format of the useful and important law of nature.
Note 2.
The law of attraction is considered universal and is possible for use in relation to any two bodies with a certain mass.
In a situation, if the mass of one interactive body turns out to be much more than the mass of the second, it is said about the particular case of gravitational force, for which there is a special term, such as "gravity". It is applicable to tasks focused on determining the strength of attraction on earth or other celestial bodies. When submitting the value of gravity in the formula of the Second Law of Newton, we get:
Here $ a $ is the acceleration of gravity, forcing the body to strive to each other. In the tasks associated with the involvement of acceleration of free fall, such an acceleration is denoted by the letter $ G $. With the help of its own integral calculation, Newton mathematically managed to prove the constant concentration of gravity in the center of the larger body.
Severity call the power with which the Earth attracts the body close to her surface .
Phenomena can be observed everywhere in the world around us. Updated up the ball falls down, abandoned in a horizontal direction stone after a while will turn out to be on Earth. Laundered from the ground a bored satellite thanks to the degree of gravity flies not in a straight line, but moves around the Earth.
Gravity It is always directed vertically down to the center of the Earth. It is indicated by the Latin letter F T. (t. - severity). Gravity is applied to the center of gravity of the body.
To find the center of gravity of an arbitrary form, you need to hang the body on the thread for different points. The intersection point of all directions marked by the thread will be the center of gravity of the body. The center of gravity of the right form is in the center of the body symmetry, and it is not necessary that it belongs to the body (for example, the rings symmetry center).
For the body of the body near the surface of the Earth, the power of gravity is equal to:
where - the mass of the earth, m. - body mass , R. - Earth radius.
If only this power is valid on the body (and all others are balanced), it makes free fall. Accelerating this free fall can be found by applying Newton's second law:
(2)
From this formula, we can conclude that the acceleration of free fall does not depend on body weight m.Therefore, it is equally for all bodies. According to the second Newton law, the strength of gravity can be determined as a product of body mass on acceleration (in this case - acceleration of free fall g.);
GravityThe body acting on the body is equal to the body weight of the body to accelerate the free fall.
Like Newton's second law, formula (2) is valid only in inertial reference systems. On the surface of the Earth, only systems associated with the poles of the Earth can be in inertial reference systems that do not participate in its daily rotation. All other points of the earth's surface are moving around the circles with centripetal accelerations and the noninercial reference systems associated with these points.
Because of the rotation of the Earth, the acceleration of the free fall on different latitudes is different. However, the acceleration of the free fall in different parts of the globe differs very little and very little differ from the value calculated by the formula
Therefore, with coarse calculations, the non-intersercial of the reference system associated with the surface of the Earth is neglected, and the acceleration of free fall is considered the same everywhere.
I did not understand the lesson in physics and I do not know how to determine the power of gravity!
Answer
The power of gravity is the property of the bodies with the mass to attract each other. Bodies that have a lot are always attracted to each other. Attraction of bodies with very large masses in astronomical scale creates significant forces, thanks to which the world is as we know.
The force of attraction is the cause of earthly attraction, as a result of which the items fall on it. Thanks to the power of attraction, the moon rotates around the earth, land and other planets - around the sun, the sunny system - around the center of the Galaxy.
In physics, gravity is the force with which the body acts on the support or vertical suspension. This force is always directed vertically down.
F - the force with which the body acts. Measured in Newtons (H).
m - body weight (weight). Measured in kilograms (kg)
g - Acceleration of free fall. It is measured in Newtons divided by kilogram (H / kg). Its value is constant and on average for the earth's surface is 9.8 n / kg.
How to determine the strength of attraction?
Example:
Let the mass of the suitcase equal to 15 kg, then to find the strength of attraction of a suitcase to the ground we use the formula:
F \u003d M * G \u003d 15 * 9.8 \u003d 147 N.
That is, the force of attraction of a suitcase is 147 Newtons.
The value G for the planet Earth is unequal - on the equator it is 9.83 N / kg, and on the poles 9.78 N / kg. Therefore, they take the average value that we used to calculate. The exact values \u200b\u200bfor different regions of the planet are used in the aerospace industry, as well as they pay attention to sports, during training athletes to participate in competitions in other countries.
Historical reference: for the first time I considered G and brought the formula for the strength of gravity, and if more precisely, the formula for the force with which the body acts on other bodies, in 1687, the famous English physicist Isaac Newton. It is in his honor and called a unit of measurement of force. There is a legend that Newton began to explore the issue of gravity after him fell on an apple head.
Absolutely on all bodies in the universe, the magic force acts, somehow attracting them to the ground (more precisely to its kernel). Nothing anywhere, nowhere to hide against a comprehensive magical burden: the planets of our solar system are attracted not only to the enormous sun, but also to each other, all objects, molecules and the smallest atoms are also mutually attracted. Also known to the little children, by the study of this phenomenon, established one of the greatest laws - the law of world community.
What is the power of gravity?
The definition and formula for a long time and many are known. Recall, the strength of gravity is a certain amount, one of the natural manifestations of the worldy gravity, namely: the force with which any body is consistently attracted to the ground.
The strength of gravity is denoted by the Latin letter F litter.
Gravity: Formula
How to calculate aimed at a certain body? What other quantities need to know in order? The formula for calculating gravity is quite simple, it is being studied in the 7th grade of the secondary school, at the beginning of the course of physics. So that it is not easy to learn, but also understand, it should be proceeded from the fact that the strength of gravity is invariably acting on the body, directly proportional to its quantitative value (mass).
The unit of gravity is named by the name of the Great Scientific, Newton.
It is always directed strictly downward, to the center of the earth's core, due to its effects all the bodies are equally falling down. Phenomena in everyday life we \u200b\u200bare watching everywhere and constantly:
- items, randomly or specially released from hand, must fall down to the ground (or any obstructive surface of the surface);
- the satellite launched into space does not fly away from our planet for an indefinite distance perpendicularly upwards, but remains to rotate in orbit;
- all rivers flow from the mountains and cannot be reversed;
- it happens, man falls and is injured;
- the smallest dust sitting on all surfaces;
- the air is concentrated at the surface of the earth;
- it's hard to wear bags;
- from the clouds and clouds dripping rain, snow falls, hail.
Along with the concept of "gravity" the term "body weight" is used. If the body is located on a flat horizontal surface, then its weight and gravity strength are numerically equal, so these two concepts often replace that not at all right.
Acceleration of gravity
The concept of "acceleration of free fall" (in other words, it is associated with the term "gravity". The formula shows: in order to calculate the force of gravity, you need to multiply the mass on G (acceleration of sv. P.).
"G" \u003d 9.8 N / kg, this is a constant value. However, more accurate measurements show that due to the rotation of the Earth, the value of the acceleration of St. n. unequal and depends on the latitude: on the northern pole it \u003d 9.832 N / kg, and at a sultry equator \u003d 9.78 N / kg. It turns out, in different places of the planet on the bodies with equal mass, the various strength of gravity is directed (the formula of Mg still remains unchanged). For practical calculations, a decision was made on minor errors of this magnitude and to use averaged value of 9.8 N / kg.
The proportionality of such a magnitude as the power of gravity (the formula proves it), allows you to measure the weight of the subject with a dynamometer (similar to the usual household bizman). Please note that the device shows only force, since it is necessary to know the regional value of "G" to determine the exact mass of the body.
Does the strength of gravity acts on any (and close, and distant) distance from the Earth Center? Newton put forward the hypothesis that it acts on the body even with a significant distance from the ground, but its value is reduced inversely in the square of the distance from the subject to the nucleus of the Earth.
Gravity in the Solar System
Does the definition and formula relative to other planets retain their relevance. With one difference in the meaning "G":
- on the moon \u003d 1.62 N / kg (six times less terrestrial);
- on neptune \u003d 13.5 N / kg (almost one and a half times higher than on Earth);
- on Mars \u003d 3.73 N / kg (more than two and a half times less than on our planet);
- on Saturn \u003d 10.44 N / kg;
- on Mercury \u003d 3.7 n / kg;
- on Venus \u003d 8.8 N / kg;
- in uranium \u003d 9.8 n / kg (almost the same as we have);
- on Jupiter \u003d 24 N / kg (almost two and a half times higher).
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