# Encyclopaedia

## Weight

One of the best-known forces is the weight of a authority, the gravitational force exerted by the earth on the authority. The terms mass and weight are often confused with each other. It is absolutely necessary to clearly understand the differences between these two physical quantities.

In science and engineering, the weight of an object is usually considered to be the force exerted on the object due to gravity. In general, gravity is a natural phenomenon by which all things with mass are brought towards each other. The mass of an object is a fundamental property. It is a numerical measure of its inertia and the measure of an object's resistance to acceleration when a force is applied. It is also a fundamental measure of the amount of matter in the object. The greater the mass, the greater the force required to cause a given acceleration. This is reflected in Newton's second law (F = m x a).

The mass of a given authority remains constant even if the gravitational acceleration acting on that authority changes. For example, an object on Earth has a certain mass and weight. When the same object is outside the gravitational field of the Earth in space, its mass remains the same but is in a "weightless" state. This means that it weighs zero in this state, since the acceleration due to gravity, and therefore the force, is zero.

Mass and weight are related:

Authorities with a large mass also have a large weight. A large stone is difficult to throw because of its large mass and difficult to lift off the ground because of its large weight. To understand the relationship between mass and weight, consider a free-falling stone with an acceleration of magnitude g (g = 9.81 m / s 2 is the acceleration due to the Earth's gravitational field). Newton's second law states that a force must act to produce this acceleration.

## Airtight

The air density ρ (also density of air or density of air) indicates the mass of air contained in a given volume. At sea level, the air is compressed more by the mass of air above it than at higher altitudes, at around 1.2041 kg/m³ at 20 °C.

## Calibration

In a calibration, the deviation of the measured value of a measuring device from a traceable, highly accurate standard is determined and documented. Under defined reference conditions and reproducible measuring procedures, the measured value of a measuring device is compared with the known value of a standard. Calibration is no intervention in the measuring device, it remains unchanged.

## Recalibration

A recalibration determines which weight class a returned weight belongs to after it has been adjusted, if necessary.

## Permeability measurement

The magnetic permeability µ (also magnetic conductivity) determines the ability of materials to adapt to a magnetic field, or more precisely the magnetization of a material in an external magnetic field. It therefore determines the permeability of matter to magnetic fields.