## 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
^{-27}kg - 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:
$K = \frac12m\vert{v^2}\vert$