Kilogram (kg)
Definition: The kilogram (symbol: kg) is the base unit of mass in the International System of Units (SI). It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10⁻³⁴ when expressed in the unit J·s, which is equal to kg·m²·s⁻¹.
History/origin: The kilogram was originally defined in 1795 as the mass of one liter of water. In 1889, the International Prototype of the Kilogram (IPK) was created. In 2019, the kilogram was redefined in terms of fundamental physical constants.
Current use: The kilogram is used globally in science, engineering, and commerce. It is the standard unit of mass in most countries around the world.
Ton (t)
Definition: A ton (symbol: t) is a unit of mass. There are three types of tons: the metric ton (1,000 kg), the short ton (2,000 lbs or 907.185 kg), and the long ton (2,240 lbs or 1,016.047 kg). Unless otherwise specified, "ton" usually refers to the metric ton.
History/origin: The ton has been used as a unit of measurement since the Middle Ages. It was originally defined as the weight of a large barrel of wine. The metric ton was introduced in 1795 as part of the metric system.
Current use: The ton is primarily used for measuring large quantities of goods, such as in shipping, construction, and agriculture. It is also used in various other applications.