# IIT JEE Main / Advanced physics 2018 Mechanics..Motion in one dimension

M O T I O N   I N  O N E   D I M E N S I O N ( pre – final draft )

Reference frame / Frame of reference : Defined as a set of axes, taken for practical purposes at being rest, which enables the position of a point ( or body ) , in space to be defined at any instant of time.To define the same,usually a set of four coordinate axes are taken,of which three are spatial and the fourth one is time. Basically of two types

• Inertial frame of reference : Here , the frame of referance is either at rest or moving with constant velocity.
• Non-inertial frame of reference : In this case, the frame of referance has some acceleration.

Reference frame in Physics : Here we look at some key points related to the utility and significance of the frames of reference in Physics.

Newton’s first law can be verified,only if the body considered is not acted on by any external forces.In such a case,what reference frame should we use ? May be , the reference frame should be fixed…… but fixed with respect to what ? . This is an important question because everything in universe is in relative motion and hence a special reference frame has to be thought of . Suppose , Newton’s first law is found to be true in a reference frame denoted F. This means that ,the above fact should be true in any other frame F′, which is mutually un -accelerated relative to F . It follows that. if a test particle has constant velocity in F , then it should have zero acceleration in F and also in F′ .

Therefore, an inertial reference frame is one in which the first law of Newton is true.The above points infer that, an exact inertial frame is not possible in nature . Now, the most practical reference frame available is EARTH . This is due to the fact that, when considering an earth bound body,the orbital acceleration of the earth is insignificant, and the effect of earth’s motion is only a small correction     read on   http://www.physicsmynd.com/?page_id=400