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What is a Frame of Reference?-Definition, And Types

August 24, 2022
written by Adeel Abbas

A frame of reference in physics consists of an abstract coordinate system and a set of physical reference points that uniquely fix the coordinate system and standardize the measurements within that frame.

What is a frame of reference?

We’ve learned about displacement, acceleration, and velocity. All of the quantities need a reference from which they are measured.

The idea of a reference frame is very different than the idea of a coordinate system. Frames can be defined by the set of rest points or the sets of simultaneous events. The frame’s ideas of space, time, rest, and simultaneity go inextricably together with that of the frame. A new coordinate system can be formed by a shift of origin or a purely spatial rotation of space coordinates. The frames don’t correspond to the classes of coordinate systems.

The frame of Reference Types

There are two types of frames of reference.

  • Inertial Frame of Reference
  • Non-inertial Frame of Reference

Inertial Frame of Reference

A frame where Newton’s law holds true is called an inertial frame of reference. That means if there is no external force on a body, it will stay at rest or remain in motion. Suppose a body is kept on the surface of the earth, for a person on the moon, it is in motion, so which is the frame of reference? The term refers to the relative position of the frame.

It is assumed that the reference frame is the inertial frame of reference. A more general definition of an inertial frame would be: Inertial frame is at rest or moves with constant velocity with respect to my assumed inertial reference frame.

Non-inertial Frame of Reference

The non-inertial frame can be defined as a frame that is accelerated with respect to the assumed inertial frame of reference. In the above example, the moon becomes a non-inertial reference frame if I assume that the earth is an inertial reference frame. We need to take some mysterious forces that are also known as pseudo forces if we want to make the law hold up.