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Monday, 26 October 2015


Today we will see very basic term of engineering, i.e. Mass and weight. My physics teacher, during my 10th standard, used to say mass of an object and weight of an object and I used to get confuse at that time. Mass and weight are not similar; both words are generally used each day in engineering life.

 Hence I have decided to write one note over mass and weight for my friends those are just started to enjoy the physics.


Mass of an object is basically defined as the amount of matter in that object. Mass will always be constant at any location and at any moment of time. Mass of an object will never be changed whether that object is at earth or at moon or at any location because that object will have same amount of matter.

Every object will have mass and it could never be zero or we may say that if you are saying that mass of a particular object is zero then its means that object does not exist in this universe. Mass is a scalar physical quantity and its unit of measurement is Kg in S.I unit system.
How you will calculate the mass of an object?

Force = Mass x acceleration
If we are applying 1 N force and object moves with an acceleration of 1 m/s2, then mass of that object will be 1 kg.

Let us see weight, what is weight of an object?

Weight of an object is basically defined as the force by which earth pulls that object towards its center. Hence we may say gravity causes the weight of an object.

Weight = Mass x acceleration due to gravity
W = M x g

As we know that mass of object will always be constant, hence weight of an object depends completely over the location as acceleration due to gravity will changes depending on the location. We must be aware that weight of an object depend will be directional proportional with acceleration due to gravity.

Weight is a vector physical quantity as it will have one direction also with magnitude and the direction will be towards center of planet where we have placed the object.

Let us see below figure, where we may see that weight of a person has two magnitudes in different condition however mass of that person is constant.

Weight of an object might be zero depending on acceleration due to gravity at location where object is placed. Unit of measurement of weight in S.I system is Newton which is indicated by “N”.