SCALARS AND VECTORS / Class11 / Physics notes NEB
All the physical quantities can be divided into two types.
They are:
(i) Scalars and
(ii) Vectors
The basic difference between them is the ′direction′.
Scalar
A physical quantity which has a magnitude but no direction is called scalar.
Example:Mass, length, temperature, time, density, work, specific heat, etc.
A scalar may be positive or negative. Scalars can be added, subtracted, multiplied or divided according to rules of ordinary algebra.
Addition and subtraction of scalars make sense only for quantities of same nature.
However, multiplication and division can be performed with different quantities.
Vector
A physical quantity which has both magnitude and direction and obey triangle law of vector addition is called vector.
Example:Velocity, acceleration, displacement, force, momentum, torque, etc.
Vectors cannot be added, subtracted, multiplied or divided according to simple rules of algebra.
Vectors can be added, subtracted or multiplied according to the rules of vector algebra.
A vector cannot be divided by another vector as it is not a valid operation in vector algebra.
A vector quantity obeys the ′triangle law of addition′ or equivalently the ′parallelogram law of addition′.
A vector is denoted by a straight line with an arrow head. The length of the line represents its magnitude and arrow head represents direction. For e.g10 N will have longer tail than 5 N along same direction .
A vector is represented as a bold face type. For example, velocity vector is represented as V. While
→
writing it is difficult to reproduce bold face type. Therefore, a vector can also be represented as V
Magnitude (scalar part) of a vector is represented as a light face type.
→
For example, magnitude of velocity vector is represented as v or .| v |
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