^Inertial & non inertial frame of reference

^Inertial & non inertial frame of reference

Accelerated frames are called non inertial & frames having zero acceleration are called inertial or Newtonian or Galilean frame of reference, thus any frame of reference at rest or moving with constant velocity with respect to a stationary frame of reference is also inertial. A frame of reference attached to an accelerating body is called non inertial frame of reference.

Suppose you are observing something which is at rest w.r.t. ground e.g. a tree, a building etc. If you observe it while staying at rest or while moving with uniform velocity w.r.t. ground, then your acceleration is zero & you are inertial frame observer. But while observing your velocity w.r.t. ground decreases or increases or changes in direction then you are said to be non inertial frame observer.

As earth is spinning about its own direction as well around the sun its speed & direction both vary over the time, hence for astronomical observations the Earth is non – inertial. However all the objects on earth have same acceleration & the relative acceleration of any one object w.r.t. other is zero, hence earth can be treated as inertial frame of reference in laboratory frame.