Explain the unit of mass in mechanics.

The unit of mass in mechanics is the kilogram (kg).

Mass is a fundamental property of matter that measures the amount of substance in an object. In mechanics, mass is a key parameter that determines an object's response to external forces. The SI unit of mass is the kilogram (kg), which is defined as the mass of the International Prototype of the Kilogram (IPK), a platinum-iridium cylinder kept at the International Bureau of Weights and Measures in France.

The kilogram is used in a wide range of applications in mechanics, from calculating the weight of an object to determining its acceleration under the influence of a force. For example, the weight of an object is given by the product of its mass and the acceleration due to gravity, which is approximately 9.81 m/s^2 on the surface of the Earth. Thus, if an object has a mass of 2 kg, its weight is 2 x 9.81 = 19.62 N.

In addition to the kilogram, other units of mass are also used in mechanics, such as the gram (g) and the tonne (t). However, the kilogram is the most commonly used unit of mass in scientific and engineering applications due to its international standardization and practicality.