Physical Quantities: In physical science the quantities we can measure
are called physical quantities.
Types of physical quantities
Physical quantities are categorized into two types. They are -
i) Fundamental quantities and
ii) Derived quantities.
Fundamental quantities: The quantities which do not depend on other
quantities are called fundamental quantities. For example: mass, length, time,
temperature, electric current, luminous intensity and amount of substance.
Derived quantities: The quantities which depend on two or more
fundamental quantities are called derived quantities. For example: Area,
Volume, Density, Speed, Velocity, Acceleration, Force, Work, Energy, etc.
According to representation types of physical quantities
According to representation physical quantities are two types. They are -
i) Scalar quantity and
ii) Vector quantity.
i) Scalar quantity: The physical quantities which can be represented
only by magnitude are called scalar quantities. For example: mass, length,
speed, work, time, temperature, etc.
ii) Vector quantity: The physical quantities whose representation needs
both magnitude and direction are called vector quantities. For example:
weight, displacement, velocity, force, electric intensity, etc. are vector
Properties of Vector
Vectors have both magnitude and direction.
Vectors can be changed by changing either magnitude or direction.
Addition, subtraction or multiplication does not follow usual mathematical
Vector multiplication depends on the angle between two vectors. The
multiplication of two vectors can be zero but neither of the vectors can be
Sign of Vectors: The representation of vectors necessitate
direction. Any vector can be representation with a letter and (a) straight
With a letter: Vectors can be represented with letters in the following
Difference between vector and scalar quantity
The physical quantity which necessitate both magnitude and direction
is called vector quantity. For example, displacement, velocity, weight
and force are vector quantities.
The physical quantity which can be represented only with magnitude is
called scalar quantity. For example, length, speed, mass and time are
A vector quantity gets changed if either its magnitude or direction or
both are changed.
Scalar quantity gets changed if only its magnitude is changed.
Addition, subtraction, multiplication of a vector quantity cannot be
done by using usual algebraic rules.
Addition, subtraction and multiplication of a scalar quantity can be done by using usual algebraic rule.
Product of two vector quantities may be zero if any of the quantities is not zero.
Product of two scalar quantities can never be zero if any of the two quantities is not zero.
Special symbol is needed to represent a vector quantity.
No special symbol is needed to represent a scalar quantity.
Product of two vectors may be a scalar or a vector quantity depending on the way of multiplication.
Product of two scalar quantities always a scalar quantity.