In order to make it convenient to work with different quantities in physics, their standard notation is used. Thanks to them, everyone can easily remember many important formulas for certain processes. In this article, we will consider the question of what g. means in physics
Gravity phenomenon
To understand what g means in physics (this topic is covered in the 7th grade of general education schools), you should get acquainted with the phenomenon of gravity. At the end of the 17th century, Isaac Newton published his famous scientific work, in which he formulated the basic principles of mechanics. In this work, he singled out a special place for the so-called law of universal gravitation. According to it, all bodies that have a finite mass are attracted to each other, regardless of the distance between them. The force of attraction between bodies with masses m1, m2 is calculated using the following formula:
F=Gm1m2/r2.
Here G - universal gravitational constant, r -the distance between the centers of mass of bodies in space. The force F is called the gravitational interaction, which, like the Coulomb force, decreases with the square of the distance, but unlike the Coulomb force, gravity is only attractive.
Free fall acceleration
The title of this paragraph of the article is the answer to the question of what the letter g means in physics. It is used because the Latin word for "gravity" is gravitas. Now it remains to understand what free fall acceleration is. To do this, consider what force acts on each body located near the surface of the Earth. Let the body have mass m, then we get:
F=Gm M /R2=mg, where g=GM/R2.
Here M, R are the mass and radius of our planet. Note that even if the body is at a certain height h above the surface, then this height is much less than R, so it can be ignored in the formula. Calculate the value of g:
g=GM/R2=6, 6710-115, 97210 24/(6371000)2=9.81 m/c2.
What does g mean in physics? The acceleration g is the value by which the speed of absolutely any body that falls freely on the surface of the Earth increases. From the calculations it follows that the increase in speed for each second of the fall is 9.81 m / s (35.3 km / h).
Please note that the value of g does not depend on the body mass. In fact, it can be seen that denser bodies fall faster lessdense. This happens because they are affected by different forces of air resistance, and not by different forces of gravity.
The formula above allows you to determine g not only for our Earth, but also for any other planet. For example, if we substitute the mass and radius of Mars into it, we get the value 3.7 m/s2, which is almost 2.7 times less than for the Earth.
Body weight and acceleration g
Above we looked at what g means in physics, it also turned out that this is the acceleration with which all bodies fall in the air, and g is also a coefficient when calculating gravity.
Now consider the situation when the body is at rest, for example, a glass is on the table. Two forces act on it - gravity and support reactions. The first is related to gravity and is directed downwards, the second is due to the elasticity of the table material and is directed upwards. The glass does not fly up and does not fall through the table just because both forces balance each other. In this case, the force with which the body (glass) presses on the support (table) is called the weight of the body. Obviously, the expression for it will take the form:
P=mg.
Body weight is a variable value. The formula written above is valid for a state of rest or uniform motion. If the body moves with acceleration, then its weight can both increase and decrease. For example, the weight of astronauts, which the booster launches into low Earth orbit, increases several times during the launch.
