Inertial and Non Inertial Frames

 For Knowing Special theory of Relativity We need to know about Frame of Reference.

 Frame of Reference

 In Physics what we do is we observe Nature, different Phenomenon's    and describe our observations, i.e where the event happened, when the event happened and this all depends on different observer's.

For ex. suppose a tree is 50 m far  from you and someone is observing that tree behind you than for that observer the tree is 50+ meters far. so we know that these things depends on observer. 

To describe a observation(event) we need to

1. describe location of event. (x,y,z)

2. describe time when event happening.

so by specifying above two , we describe event as , a chalk is at distance(x,y,z) w.r.t me at time t.

So a Frame of reference is

something using which we specify event.

A frame of reference consist.

X , Y , Z mutually perpendicular axes. With origin as Observer

and something say a clock to measure time.

all these combined make a frame of reference.

implies a observer with x, y, z axes and a clock is a frame of reference.

Types Of Frame Of Reference.

In Physics We all know newton's laws of Motion also 1st law.             if you are a good observer ( a physics student must be) you must observed that in some cases newton's first law appears to be invalid.  

 if  You not observes don't worry,  Visualize the condition i am telling you, you are sitting in running bus and you see that when the bus stopped all passengers experience jerk forward, but w.r.t you there is no force acted on you, 

So as Per 1st Law you should not experience jerk at all, but in reality you experienced.

 

Therefore We arrive at the point that there are some frame of references(such as accelerating bus's frame of reference) From which Newton's First law does not Hold Good.

From above discussion we concluded two types of frame of references:-

1.Inertial Frame of Reference                                                               a frame of reference from which newton's First Laws Holds Good.     by observing we say that all non-accelerating frames are inertial frames.

2.Non Inertial Frame of Reference                                                         a frame of reference from which newton's first law does not valid (not holds good), all non inertial frame of reference are non inertial frames.

Now for applying newton's first law from non inertial frames , we apply an additional Pseudo Force to object under study from non inertial frame. F= -ma  in vector form,

where a = acceleration of observer w.r.t any inertial frame.

You Can Watch this video for more examples in detail

                     

 Video by Prof. HC Verma 

Allowance made for fair use purpose.