Hi
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Scalars:
Some physical quantities can be described just by their numerical value (with their respective units) without directions (they don’t have any direction). The addition of these physical quantities follows the simple rules of algebra. Such physical quantities are known as scalars.
Example:
It is a scalar quantity and unit of mass is kg. If you are adding up two masses, let’s say: 5kg and 7kg, the total mass of the system will by (5 + 7) kg = 12kg
Other common examples of scalar quantities are: Temperature, Length, and Speed
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Vectors:
Sometimes, to describe certain physical quantity, complete description of magnitude and direction is required (unlike scalars, they have a direction). The addition of these physical quantities does not follow the rules of algebra. To add vector quantities, special rules for the addition and subtraction of vectors are followed which we will learn as we go ahead in this chapter. These physical quantities are known as vectors.
Example:
Velocity is a vector quantity since it has both magnitude (numerical value) and direction. If you are saying that the velocity of a certain object is 5 m/s, it is incomplete since the direction of velocity is not mentioned. Velocity could be in any direction, so a certain direction has to be assigned to it in order to give complete information.
Other common examples of vector quantities are: Acceleration, Linear momentum and Force