The document discusses frames of reference in physics. It defines a frame of reference as the perspective from which the position or motion of an object is described. Frames of reference are either inertial or non-inertial. Inertial frames are where Newton's laws hold true - an object either remains at rest or in motion with constant velocity unless acted on by an external force. Non-inertial frames include accelerated or rotating frames where Newton's laws do not apply, such as reference frames on the surface of the rotating Earth.

1. CLASS-BSC(CS)1ST YEAR
PHYSICS
SUBMMITTED BY SUBMMITTED TO
SHIVANI AGRAWAL GYAN RAO DHOTE SIR

2. FRAMES OF REFERENCE
 The frame relative to which the position or the motion
of a body is specified is called the frame of reference.
The position of other objects is specified relative to the
frame of reference being assumed to be connected
with a rigid body. For this, a convenient point is chosen
as the position vector of the body from the origin.
Generally, the observer is considered to be coinciding
with the origin.
 The frame of reference are of two kinds:
 1) Inertial frames of reference.
 2)Non-inertial frames of reference.

3. INERTIAL FRAMES OF REFERENCE
 The frames of reference in which the Newton’s law
holds, are called the inertial frames. According to
Newton’s law, a body not acted upon by any external
force, has an uncelebrated motion.
 In other words, if the body is at rest, it remains at rest,
but if it is in motion, it remains moving with the same
speed in the same direction unless an external force is
applied.
 Example: If no external force acts on a body, its
acceleration remains zero.

7. Inertial frame of reference
 Mathematically, if F = o in an inertial frame a=0
OR

8.  An observer in each inertial frame has the same
description of physical events. In other words the
frame S and S’ are said to be inertial only if the
acceleration of a body measured by the observers in
both frames is same.
 Consider two frames S and S’ either stationary relative
to each other or moving with a constant velocity
relative to each other. A body which is stationary to an
observer in a frame S, will either appear to be
stationary or will appear to be moving with a constant
velocity to an observer in the frame S’ also.
 Ex; the force acting on the body for the observers of
both the frames will be zero.

9. sSimilarly, if a body is moving with some
acceleration relative to the observer in the
frame S, the body will have the same
acceleration relative to the observer in the
frame S’. Thus, all those frames of reference
which are either stationary relative to each
other or are in uniform motion are called the
inertial frames provided that one of these
frames is inertial.

10. NON-INERTIAL FRAMES OF
REFERENCE
 The frames of reference in which Newton’s laws are not
valid, are called the non-inertial frames. All the
accelerated and rotating frames are non- inertial. Since
our earth rotates around its own axis, it is a non-
inertial frames.