# Suppose you observe an object from a certain reference system and find that when forces do not...

## Question:

Suppose you observe an object from a certain reference system and find that when forces do not act on it, the body has an acceleration. How can you use this information to find an inertial reference system?

## Inertial Frames of Reference:

Those frames in which laws of physics, or specifically Newton's laws of motion do not change are called as the inertial frames of reference.

In vertical motion under gravity, the accelerations of the bodies due to gravity up to terrestrial heights is always approximately remains constant and is {eq}9.8 \ m/s^{2} {/eq}

Now, there are very less examples of the case when net force on an object is zero but still there is a non-zero value of acceleration. And vertical motion is one of them. Therefore, it is the case when a projectile thrown upwards, as noticed from the ground frame (inertial frame of reference), attains its final maximum height, its final velocity at that instant becomes zero which means a constant velocity and constant velocity means that net force on the object is zero, only for that instant as deduced by Newton's 1st law of motion but the acceleration for it is still {eq}9.8 \ m/s^{2} {/eq}.

That's it. 