# Mass and Weight

Mass is the one of the most significant fundamental quantity of an object in physics and is one the basic property of matter thus is defined as the measure of the amount of matter that is present in a body or substance.

The SI (international system of units) unit of mass is kilograms(kg). The mass of a body does not change it only changes when a huge amount of energy is given or taken from the body for instance in nuclear reaction a huge amount of energy is produced from a certain amount of matter and this lessens the mass of the matter.

The more mass an object has the more force it takes for it to get moving. The symbol of mass is m or M. Various physical quantities like Force, Inertia, and Relative theory of Einstein’s also depend upon mass.

E = mc2

There are various ways of determining the quantity of mass the most used are inertial mass and gravitational mass.

## Inertial Mass

It is defined as the mass which is determined by how much an object could resist to acceleration. For instance, if we push two objects with the same amount of force and under the same conditions then object which have lower mass will accelerate faster than the object with the heavy mass.

### Gravitational Mass

Gravitational mass is defined as the measurement of how much gravity an object employs on other objects or measurement of how much gravity an object experiences from other objects.

#### Centre of Mass

Centre of mass of a body can be defined as a point where all the mass of the object is concentrated.

##### Atomic Mass Unit

The atomic mass unit is used is used to measure the mass of atoms and molecules which are so small, that the kilograms is not so appropriate to use for measurement. One atomic mass unit can be defined as 1/12 the mass of a carbon: 12 atoms.

The value of 1 atomic mass is 1.66 x 10-27..

###### Mass Conservation

Mass Conservation means that the mass of reactants in the reaction is always equal to the mass of its products.

For Example; An example of law of conservation of mass is coal, the carbon atom in coal becomes carbon dioxide when it is burned or ignited. Thus, carbon atom changes from a solid structure to a gas but the mass of the substance does not change.

###### Characteristics of Mass

• Mass cannot be zero as everything around us has some mass.

• Mass is measured in grams, kilograms, or milligrams.

• Mass is a scalar quantity which means it only has magnitude.

###### Weight

Weight is defined as the measure of the force of gravity acting on an object.

S.I unit of weight is Newtons(N). Weight is the measure of the acceleration of gravity

W = mg

In the above expression g is the gravitational field which is equal to 9.8 and/kg and m is denoted as mass.

###### Characteristics of Weight

• Weight can be measured by via a spring balance.

• Weight can be zero.

• Weight is a vector quantity. Thus, it has both direction and magnitude

###### Difference Between Mass and Weight
 Mass Weight Mass is a scalar quantity which means it only has magnitude Weight is a vector quantity which means it has both magnitude and direction Mass is measured in kilogram, gram, and milligrams Weight is measured in Newtons (N) Mass can never be zero Weight can be zero Mass is not dependent on the gravity and is same everywhere Weight is a physical property that is dependent on gravity and it vary from place to place Mass can be measured with the help of several instruments such as beam balance etc. Weight can be measured with the help of spring balance
###### Relation Between Mass and Weight

The weight of the body can be defined as the force exerted by the earth or any other celestial object on other object.

In case of earth when a body falls towards the earth, the force of gravitation pulls the object with an acceleration denoted as`g`.

According to Newton’s second law, the force of attraction on the body of mass m is F=Mass x Acceleration due to gravity = mg This is force on the object and it is called weight. Thus, W=mg

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