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LESSON NOTES

What is Mass?
It is one of the fundamental quantities in Physics and the most basic property of matter.
We can define mass as the measure of the amount of matter in a body. The SI unit of
mass is Kilogram (kg).
It is a scalar quantity. Its symbol is m.

Mass of a body can never be zero.

Note: The mass of a body does not change at any time. Only for certain extreme cases
when a huge amount of energy is given or taken from a body. For example, in a nuclear
reaction tiny amount of matter is converted into a huge amount of energy, this reduces
the mass of the substance.

What is Weight?

It is the measure of the force of gravity acting on a body.

It is a vector quantity.
Weight of a body can be zero. It is zero at the center of the earth.

The formula for weight is given by:

w = mg
As weight is a force its SI unit is also the same as that of force, S.I unit of weight is
Newton (N). Looking at the expression of weight we see that it depends on mass and
the acceleration due to gravity, the mass may not change but acceleration due to gravity
does change from place to place. To understand this concept let’s take this example,
Shape of the earth is not completely spherical, but an oblate spheroid, therefore a
person standing at the equator is far away from the center of the earth than a person
standing at the north pole, as acceleration due to gravity is proportional to the inverse of
square of the distance between two objects, a person standing at the north pole would
experience more weight as he is closer to the center of the earth than a person standing
at the equator.

What is the Difference between Mass and Weight?

Mass Weight

Weight can be zero. As in space if no gravity acts upon
Mass can never be zero.
an object, its weight becomes zero.

Mass is a scalar quantity. It Weight is a vector quantity. It has magnitude and is