This document discusses inertial frames of reference and defines them as frames of reference where Newton's laws of motion hold. It provides several descriptions of inertial frames, including that they have constant velocity or are non-accelerating. The document proves that two frames moving at a constant velocity relative to each other will measure the same acceleration for objects, showing that both frames are inertial. It concludes that any frame with the same constant velocity as an inertial frame is also inertial.

2. RAI SAHEB BHANWAR SINGH
COLLEGE
RALA, NASRULLAGANJ
CLASS- B.Sc (5th Sem)
SUBJECT- PHYSICS
PRESENTATION
 Guided By- Mr Gyanrao
Dhote
 Student Name- Kamini
Malviya

3. INERTIAL FRAME OF
REFERENCE

4. •DEFINITION
The frames of reference in which
the Newton’s law holds are called
the Inertial frames.

5. According to Newton’s law, a body not acted
upon by any external force, has an
unaccelerated motion (i.e., if no external
force acts on a body, its acceleration
remains zero). 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.

6. Mathematically, if F=0, in an
inertial frame, a=0
or dr/dt=0
or dx/dt=0,
dy/dy=0 and dz/dt=0

7. Inertial frames of reference
1.Inertia is a property of matter.
2.It is that property of matter which opposes
changes in velocity.
So, one must centre one’s physics on these
thoughts:
An object’s velocity will not change all on its own.
Pushes, or pulls, are necessary to change an object’s
velocity.

8. There are several ways to
describe an inertial frame. Here
are a few discriptions:
1.An inertial frame of reference is a frame of
reference with constant velocity.
2. An inertial frame of reference is a non-
accelerating frame of reference.

9. 3.An inertial frame of reference is a
frame of reference in which the law of
inertia holds.
4.An inertial frame of reference is a
frame of reference in which Newton’s
laws of motion hold.
5.In an inertial frame of reference no
fictitious forces arise.

11. 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, i.e., the force acting on
the body for the observers of both the

12. frames will be zero. Similarly, if a
body is moving with some
acceleration a relative to the
observer in the frame S, the body
will have the same acceleration(= a)
relative to the observer in the
frame S’.

13. Proof: In Fig., S is an inertial frame and
another frame S’ is moving with a
constant velocity v relative to the frame
S. Initially (at t=0 ), the origin of both
the frames coincide. At any instant t,
the position vectors r and r’ of the
partical P in the frames S and S’
respectively are related as follows:

14. r’= r – vt
In Fig., in the vector triangle OO’P,
OP= OO’+O’P
or r = vt + r’
or r’= r – vt
The velocity of the partical in frame S’ is
dr/dt= dr/dt-v
and acceleration of the particle in frame S’
is
dr’/dt= dr/dt or a’= a

15. Thus, a particle experiences a the
same acceleration in frames S and
S’ moving with a constant velocity
relative to each other. If the
acceleration of the particle is zero
in a frame S, its acceleration will
also be zero in the frame S’. Since
the frames S is inertial, the frame S’
will also be inertial.

16. THANK YOU