Question

Define inertial frame and non-inertial frame. Is earth an inertial frame of reference?

Answer 1

Hint:We know that a frame of reference is a system which consists of an abstract coordinate system and the set of physical reference points. These two uniquely fix the coordinate system and standardize measurements within that frame. This system determines positions and velocities of objects in that frame. Also, it is important to know that different reference frames move relative to one another. In this question, we will first define two types of reference frame and then understand whether earth is an inertial frame or not.

Complete answer:
We will first define an inertial frame. The frame of reference where Newton’s law is applicable is called an inertial frame. In other words, until and unless an external force is acting on a body, it will stay at rest or remain in uniform motion.Now we will define a non-inertial frame. A frame which is accelerated with respect to the assumed inertial frame of reference is called a non-inertial frame.

In these frames, Newton’s law will not be applicable.Now, according to these definitions, we will determine whether the earth is an inertial frame or not. We know that the earth rotates around its axis and also revolves around the sun. In both these motions, centripetal acceleration is present. Therefore, earth or any frame of reference fixed on earth cannot be taken as an inertial frame. Thus, earth cannot be considered as an inertial frame of reference.

Note:We can define both the frames in other words also. For example, an inertial frame of reference can be defined as a frame of reference either at rest or moving with a uniform velocity or zero acceleration. Whereas, a non-inertial frame of reference can be defined as a frame of reference which is either having a uniform linear acceleration or is being rotated with uniform speed. A non-inertial frame is also called an accelerated frame.