Rest and Motion of an object

Have you ever thought about the actual meaning of “rest “or “motion”? When do we say that a body is in rest/motion?

You can tell that “the body is at rest”, if it’s position is not changing with time. Also “it is moving” if it’s position is changing with time.

However, Can you surely tell that the table infront of you is at rest? The answer is “No”. you know that our earth is moving continuously. So your home, Table, books…..etc. are moving with earth. When we are looking from moon we will tell that all things in earth are moving.

So we can conclude that, the motion is a dependent property on viewer or observer.

This means that, we cannot study an object without the observer.

Here comes “frame of reference”. To locate the position of a particle we need a frame of reference. It is actually an eye of an observer. It will give the position (x, y and z coordinates from an origin) of body at that time (which can be taken from the clock running in background).

If all the three coordinates of a particle remain unchanging with time we can tell that the body is in rest with respect to that frame of reference.

If all the three coordinates of a particle are changing with time we can tell that the body is in motion with respect to that frame of reference.

There is no rule on selecting frame of reference. We can select as per our convenience.
Stay online,we have just started from the basics.