# Physics Lesson 1.2.2 - Mass

Welcome to our Physics lesson on Mass, this is the second lesson of our suite of physics lessons covering the topic of Length, Mass and Time, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.

## Mass

Mass is the quantity of matter a body contains, as measured by its acceleration under a given force or by the force exerted on it by a gravitational field (see the concepts of force, acceleration and gravitational field in the corresponding articles).

For now, we can only limit in the "quantity of matter" in explaining the meaning of mass. Thus, since all materials are composed by tiny particles (atoms and molecules), their number contributes in making a certain object more massive (heavier) or less massive (lighter). A massive (heavier) object has a very large number of atoms than a less massive (lighter) one.

In the SI system, the unit of mass is kilogram (kg). But why is kilogram (a multiple of gram) used as a base unit for mass instead of gram? The answer is: for political reasons.

Kilogram is also an arbitrary established unit of mass. The mass of a cylinder of platinum-iridium alloy kept in the International Bureau of weights and measures preserved at Serves near Paris, is called one kilogram.

In the original metric system, the unit of mass was the grave, which was equal to 1000 grams. Since the gram itself was too small to be measured reliably, it was not practically used as the standard, so the larger grave was the unit of mass.

Grave was not used anymore after the French Revolution for political reasons. The old grave unit was replaced with its equivalent: 1000 grams, which could also be named a kilogram using the system of prefixes.

The units of mass also change by the powers of ten. We use one of the prefixes discussed in the article "Units. Systems of Units. Fundamental and Derived SI Units" to express multiples and submultiples of gram (the main unit kg is one of them). They are:

ton (t) = 1000 kg = 103 kg
quintal (q) = 100kg = 102 kg
hectogram (hg) = 10-1 kg
decagram (dag) = 10-2 kg
decigram (dg) = 10-4 kg
centigram (cg) = 10-5 kg
milligram (mg) = 10-6 kg
microgram (μg) = 10-9 kg

## More Length, Mass and Time Lessons and Learning Resources

Units and Measurements Learning Material
Tutorial IDPhysics Tutorial TitleTutorialVideo
Tutorial
Revision
Notes
Revision
Questions
1.2Length, Mass and Time
Lesson IDPhysics Lesson TitleLessonVideo
Lesson
1.2.1Length
1.2.2Mass
1.2.3Time
1.2.4Dimensional Analysis

## Whats next?

Enjoy the "Mass" physics lesson? People who liked the "Length, Mass and Time lesson found the following resources useful:

1. Mass Feedback. Helps other - Leave a rating for this mass (see below)
2. Units and Measurements Physics tutorial: Length, Mass and Time. Read the Length, Mass and Time physics tutorial and build your physics knowledge of Units and Measurements
3. Units and Measurements Video tutorial: Length, Mass and Time. Watch or listen to the Length, Mass and Time video tutorial, a useful way to help you revise when travelling to and from school/college
4. Units and Measurements Revision Notes: Length, Mass and Time. Print the notes so you can revise the key points covered in the physics tutorial for Length, Mass and Time
5. Units and Measurements Practice Questions: Length, Mass and Time. Test and improve your knowledge of Length, Mass and Time with example questins and answers
6. Check your calculations for Units and Measurements questions with our excellent Units and Measurements calculators which contain full equations and calculations clearly displayed line by line. See the Units and Measurements Calculators by iCalculator™ below.
7. Continuing learning units and measurements - read our next physics tutorial: Significant Figures and their Importance