What is mass?

Mass is a fundamental physical property of matter, and also a measure of an object's inertia when subjected to force. Mass determines the degree of an object's influence in a gravitational field, meaning it affects the attractive forces between objects. In the International System of Units (SI), the standard unit of mass is the kilogram (kg).

Are mass and weight the same thing?

Although mass and weight are often confused in everyday life, they are actually two different concepts.

• Mass It is the amount of matter an object possesses, which remains unchanged regardless of its location.
• Weight It is the force that an object experiences due to the influence of gravity, depending on where the object is located.

For example, an object with a mass of 10 kg will always maintain this value whether it is on Earth or the Moon. However, its weight will decrease if placed on the Moon because the gravitational force there is weaker than on Earth.

The concept of mass in physics

In classical mechanics, mass is simply understood as the amount of matter contained in an object. However, when an object moves at very high speeds (close to the speed of light), Einstein's special theory of relativity indicates that the object's kinetic energy can contribute to an increase in its mass. This leads to the conclusion that mass is not just a fixed quantity but is also related to energy.

Types of mass in physics

• Inertial mass – Represents the degree of resistance to a change in an object's motion when a force is applied, based on Newton's law (F = ma).
• Active gravity – To measure the ability of an object to create a gravitational force that acts on another object.
• Passive gravitational mass – To measure the degree to which one object is affected by the gravitational force of another object.

Despite various measurement methods, physics experiments have shown that all these types of mass have equivalent values.

Formulas for calculating mass and gravitational force

When an object has mass m, subjected to force FIts acceleration is calculated using the formula:

a = F / m

If two objects have mass m₁ , and m₂, separated by a distance rThen the gravitational force between them is calculated as:

F = G * (m₁ * m₂) / r²

Inside, G The gravitational constant has a value of approximately 6,67 × 10⁻¹¹ N·m²/kg².

Table of units of mass measurement

Ton	Tạ	Yen	Kilogram (kg)	Hectogram (hg)	Decagam (dag)	Gram (g)	Centigram (cg)	Milligram (mg)
1	10	100	1000	10,000	100,000	1,000,000	10,000,000	1,000,000,000

How to convert units of mass

To convert between units of mass, remember that each preceding unit is ten times larger than the unit following it. For example:

• 1 quintal = 10 yens
• 1 yến = 10 kg
• 1 kg = 10 hg

Note when converting units of mass

When converting units of mass, pay attention to the units in the 10-point scale to avoid confusion. For non-SI units such as pounds or ounces, specific conversion factors must be used.

Mass measuring instruments

Common instruments for measuring mass include:

• Mechanical scales
• Electronic scales
• Spring balance
• Digital scales