Weight. In Physics terms , weight is the force of a body acting on a support point, caused by the acceleration of gravity , when it acts on the body’s mass. Weight is itself a vector quantity , so it is characterized by its magnitude and direction, applied at the body’s center of gravity and directed roughly towards the center of the Earth .
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- 1 Weight and mass
- 2 weight units
- 1 International System of Units
- 2 Technical Unit System
- 3 Other Systems
- 3 Weight calculation
- 4 Sources
Weight and mass
The mass of a body is a characteristic property of it, which is related to the number and class of the particles that make it up. It is measured in kilograms (kg) and also in grams, tons, pounds, ounces, etc.
The weight of a body is the force with which it is attracted to the Earth and depends on its mass. One body of mass twice as much, it also weighs twice as much. It is measured in Newtons (N) and also in kg-force, dynes, pound-force, ounce-force, etc.
The kg is therefore a unit of mass , not weight. However, many devices used to measure weights (scales, for example), have their scales graduated in kg instead of kg-force. This is usually not a problem, since 1 kg-force is the weight on the Earth’s surface of an object of 1 kg mass.
Therefore, a person weighing 60 kg weighs 60 kg-Force on the Earth’s surface. However, the same person on the Moon would weigh only 10 kg-force, although his mass would still be 60 kg. (The weight of an object on the Moon represents the force with which it draws it)
International System of Units
The physical quantities are expressed in units of the international system of units (SI). Thus, the weight is expressed in SI force units, that is, in newtons (N): 1 N = 1 kg. 1 m / s²
Technical System of Units
In the Technical System of Units , weight is measured in kilogram- force (kgf) or kilopond (kp), defined as the force exerted on a kilogram of mass by the acceleration in free fall (g = 9.80665 m / s²)  .
So: 1kp = 9.80665 N = 9.80665 kg.m / s²
Weight is also often indicated in other systems, such as dyna, pound-force, ounce-force, and so on.
The calculation of the weight of a body from its mass can be expressed using the second law of dynamics :
Where the value of is the acceleration of gravity (see) in the place where the body is. In the first approximation, if we consider the Earth as a homogeneous sphere, it can be expressed with the following formula: