Relative Motion
Also,
Note that 
have zero derivatives with respect to time as these are constant vectors. Their direction and magnitude both remain constant with respect to time. They only translate.
A translating reference frame which has no acceleration is known as inertial frame.
An example: A card board is moving in plane floor with a velocity 
with respect to some fixed X-Y axes. A particle is rotating in a circle of radius 2 units with a speed of 5 rad/sec. What is the absolute(with respect to X-Y) velocity of particle when the particle is at P ?
with respect to some fixed X-Y axes. A particle is rotating in a circle of radius 2 units with a speed of 5 rad/sec. What is the absolute(with respect to X-Y) velocity of particle when the particle is at P ? Solution:
