Question

How do you define mass and weight? Describe their characteristics.

Answer 1

Characteristics of mass

1. Mass is the physical quantity which is a measure of inertia.
2. Mass can be defined as the quantity of matter contained in a body.
3. Units of mass -
   1. gram (in C.G.S. units)
   2. kilogram (in S.I. units)
4. It is a scalar quantity.
5. It remains constant wherever the body may be taken.
6. It is independent of the nature and position of bodies in the surroundings.
7. Mass of a body can be compared with that of a certain standard by a common balance.

Characteristics of weight

1. Weight can be defined by the force with which a body is attracted towards the centre of the earth.
2. Mathematically it can be expressed as - $W=m\times g$.
3. Units of force are -
   1. dyne or gram-force (gf) in C.G.S. system
   2. newton or kilogram-force (kgf) in S.I. system
4. It is a vector quantity and always acts towards the centre of the earth..
5. It can be determined with the help of a spring balance.

Comparison between Mass and Weight
Mass	Weight
It is the amount of matter contained in a body.	It is the force with which a body is attracted towards the centre of earth.
It is a scalar quantity.	It is a vector quantity.
In SI, it is measured in kg.	In SI, it is measured in newton.
It is a constant quantity.	It may vary from place to place since it depends upon the value of ‘g’ at a place.
It is never zero for a material body.	It is zero at the centre of earth. It may also be zero in some special circumstances.
It is an essential property of material bodies.	It is not an essential property of material bodies.