Physics

# Reference frame & Principle of relativity

In this post, we are going to discuss the reference frame and principle of relativity. The principle of relativity was given by Albert Einstein in 1915.
A reference frame is a space in which we are making observations and measuring physical quantities. There are two types of reference frames: the inertial reference frame and the noninertial reference frame.

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## Types of Reference frames :

• Inertial Reference Frames are the frame of references in which Newton first law of motion holds i.e. an object at rest and an object in motion remains in motion unless acted by a net force. An inertial reference frame is either at rest or moves with a constant velocity.
• noninertial reference frame is a frame of references that is accelerating, either in a linear fashion or rotating around some axis.
Examples: Label the type of reference frames :
1. A train moving with constant velocity. (Inertial)
2. A rotating merry-go-round. (Non-Inertial)
3. A turning car with constant speed (Non-Inertial)
4. The rotating Earth (Non-Inertial)
The principle of Relativity :
The principle of relativity states the basic laws of physics are the same in all inertial frame of references. This is as you go from one reference frame to another, things like forces, mass, length and time do not changes. These quantities are said to be absolute.
Since all the laws of mechanics do not change for different inertial reference frames, no one inertial reference frame is special in any sense. Therefore we conclude that :
“All Inertial frame of references are equivalent”.