SCALAR AND VECTOR QUANTITIES

◆SCALAR AND VECTOR QUANTITIES◆

●Various quantities used in mechanics may be grouped into scalars and vectors.

●A quantity is said to be scalar, if it is completely defined by its magnitude alone.

●Examples of scalars are length, area,time and mass.

●A quantity is said to be vector if it is completely defined only when its magnitude as well as
direction are specified.

●The example of vectors are displacement, velocity, acceleration, momentum, force etc.

Unit MKS, CGS, FPS

◆ UNITS ◆

      •Length (L), mass (M) and time (S) are the fundamental units used in mechanics.

       •The units of all other quantities may be expressed in terms of these basic units.

The three commonly used systems are

— Metre, Kilogram, Second (MKS)
— Centimetre, Gram, Second (CGS)
— Foot, Pound, Second (FPS).

The systems are named after the units used to define the fundamental quantities length, mass
and time. Using these basic units, the units of other quantities can be found. For example in MKS
the units for various quantities are

Quantity           Unit
Area                  m2
Volume             m3
Velocity            m/sec
Acceleration.   m/sec2
Momentum      kg-m/sec  [Since it is = mass × velocity]
Force                 kg-m/sec2 [Since it is = mass × acceleration]