# Has gravity mass

## Strength and mass; Location factor

#### Cause of weight force

In the Greek theory of nature one justified the falling of a body with the help of "natural movements". Even before Galileo and Newton it was clear that the weight - causing the fall - can be explained by gravity:

A body on the surface of the earth is attracted to the earth. The acting force is called gravity or weight \ ({F _ {\ rm {G}}} \).

#### Interaction principle

The weight force is not a physical property, i.e. it does not only depend on the observed body, but also on the celestial object on which the body is located. The weight "therefore includes two" that interact with one another. This also corresponds to Newton's principle of interaction. It says that the body then also exerts an equal but opposite force on the earth (actio opposite reaction).

#### Ways of speaking

Since the celestial body is one of the decisive factors for the weight, the phrase: "The body has the weight" should be replaced by the expression "The body experiences the weight". In everyday life, weight force is also referred to as "weight" for short.

#### Law of gravity

Newton recognized this as the deeper cause of the weight force Mass attraction or Gravity:

The law of gravity describes the forces between two bodies 1 and 2 with the masses \ (m_1 \) and \ (m_2 \), whose centers of gravity are at a distance \ (r \) from each other. We denote the two forces with \ ({\ vec F} _ {12} \) (force that body 1 exerts on body 2) and \ ({\ vec F} _ {21} \) (force that body 2 exercises on body 1); according to Newton's 3rd axiom, the two forces are directed in opposite directions and have the same amount, ie \ (F = \ left | {{{\ vec F} _ {12}}} \ right | = \ left | {{{\ vec F} _ {21}}} \ right | \).

The following simulation shows the basic dependency of the two forces \ ({\ vec F} _ {12} \) and \ ({\ vec F} _ {21} \) on the masses \ (m_1 \) and \ (m_2 \ ) as well as their distance \ (r \).