The quantities measured in Physics may be
divided into two groups:
(a) scalars - these are quantities that have magnitude (size)
only.
Examples of scalars are length, speed, mass, density, energy, power, temperature,
charge, potential difference
(b) vectors - these are quantities that have direction as
well as magnitude.
Examples of vectors are displacement, force, torque, velocity,
acceleration, momentum, electric current, magnetic flux density, electric field
Scalars may be added together by simple arithmetic but when two or more vectors
are added together their direction must be taken into account as well.
A vector may
be represented by a line, the length of the line being the magnitude of the vector and the
direction of the line the direction of the vector.
When people say that a vector has a
direction it means that either it is moving in a certain direction (as in a velocity) or that it could
produce movement in a certain direction (as in a force or a magnetic field).
