Mass

Mass is a physical property of matter that depends on size and shape of matter, and is expressed as kilograms by the SI system.

Learning Objective

Justify the significance of understanding mass in physics

Key Points

Mass is defined as a quantitative measure of an object's resistance to acceleration.
According to Newton's second law of motion, if a body of fixed mass m is subjected to a single force F, its acceleration a is given by F/m.
Mass is central in many concepts of physics, including:weightmomentumaccelerationkinetic energy.
According to Newton's second law of motion, if a body of fixed mass m is subjected to a single force F, its acceleration a is given by F/m.

Term

mass
The quantity of matter which a body contains, irrespective of its bulk or volume. It is one of four fundamental properties of matter. It is measured in kilograms in the SI system of measurement.

Example

In theoretical physics, a mass generation mechanism is a theory which attempts to explain the origin of mass from the most fundamental laws of physics. To date, a number of different models have been proposed which advocate different views at the origin of mass. The problem is complicated by the fact that the notion of mass is strongly related to the gravitational interaction but a theory of the latter has not been yet reconciled with the currently popular model of particle physics, known as the Standard Model.

Full Text

What is Mass?

All elements have physical properties whose values can help describe an elements physical state. Changes to these properties can describe elemental transformations. Physical properties do not change the chemical nature of matter. The physical property we are covering in this atom is called mass.

Mass is defined as a quantitative measure of an object's resistance to acceleration. The terms mass and weight are often interchanged, however it is incorrect to do so. Weight is a different property of matter that, while related to mass, is not mass, but rather the amount of gravitational force acting on a given body of matter. Mass is an intrinsic property that never changes.

Units of Mass

In order to measure something, a standard value must be established to use in relation to the object of measurement. This relation is called a unit. The International System of Units (SI) measures mass in kilograms, or kg. There are other units of mass, including the following (only the first two are accepted by the SI system):

t - Tonne ; 1t = 1000kg
u - atomic mass unit ; 1u ~= 1.66x10^-27kg
sl - slug
lb - pound

Concepts Using Mass

Weight - see
Newtons Second Law - mass has a central role in determining the behavior of bodies. Newtons Second Law relates force f, exerted in a body of mass m, to the body's acceleration a:F=ma
Momentum - mass relates a body's momentum, p, to its linear velocity, v:p = mv
Kinetic Energy - mass relates kinetic energy, K to velocity, v: $K = \frac12m\vert{v^2}\vert$

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