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Measurement of Physical Quantities

Fundamental quantities and international system of units

We measure many articles in our everyday life such as the weight of vegetables, the volume of milk, the speed of a car etc. These quantities such mass, weight, distance, temperature, etc that can be expressed in numbers are known as physical quantities. A value and a unit are used to express the magnitude of a physical quantity.

Can all the quantities be described only by its magnitude?

There are some physical quantities that can be described only by its magnitude. They are called scalar quantities. While there are some that require direction along with its magnitude. They are called vector quantities.

How are mass and weight different quantities?

To measure the mass of an object, we only have to know how much matter is present in the object. Therefore, the mass of an object is a physical quantity that only requires magnitude to be expressed. Therefore, we say that mass is a scalar quantity.

Whereas the weight of an object is the gravitational pull of the earth acting on the mass of the object towards the earth's centre. So to measure weight, we require direction as well as magnitude which makes it a vector quantity.  The weight of an object can be different at different places but the mass of an object remains same. For instanc…

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