Mass
Mass measures inertia and gravitational attraction.
Mass is an intrinsic positive physical quantity of a body, which measures its resistance to acceleration. In modern physics, it is generally defined as the strength of an object's gravitational attraction to other bodies, as measured by an observer moving along at the same speed. The unit of mass in the International System of Units (SI) is the kilogram (kg).
- field
- Physics
- unit
- Kilogram (kg)
- defined_by
- Planck constant, speed of light, and definition of the second
- key_principle
- Equivalence of inertial and gravitational mass
- known_for
- Resistance to acceleration and gravitational attraction
Lore & Background
Mass can be experimentally defined as a measure of a body's inertia, meaning the resistance to acceleration when a net force is applied. In the Standard Model of physics, the mass of elementary particles is believed to be a result of their coupling with the Higgs boson in what is known as the Brout–Englert–Higgs mechanism. There are several distinct phenomena used to measure mass: inertial mass, active gravitational mass, and passive gravitational mass. Although some theorists have speculated that some of these phenomena could be independent of each other, current experiments have found no difference in results regardless of how it is measured.
Reader's Guide
Mass is a fundamental concept in physics, distinct from weight, which is a force. In everyday usage, mass and weight are often used interchangeably, but conceptually mass (measured in kilograms) refers to an intrinsic property of an object, whereas weight (measured in newtons) measures an object's resistance to deviating from its current course of free fall.
Did You Know?
- Mass is not the same as weight; an object on the Moon would weigh less than on Earth but still have the same mass.
- The unit of mass in the International System of Units (SI) is the kilogram (kg).
- In the Standard Model, the mass of elementary particles is believed to result from their coupling with the Higgs boson.
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