1. Motion

If something (let’s call it object A) is changing its position compared to something else (we’ll call this object B), then we say object A is in motion relative to object B.

Object B is what we call the Frame of Reference, or just the Frame. It’s like the fixed point or background you’re using to judge if something is moving.

Examples:

1. Car on a Road: If you’re talking about a car driving, you’d usually compare its movement to the starting point of the road. That starting point is your Frame of Reference.
2. Tea-seller on a Train: If you’re describing a tea-seller walking around inside a moving train, you might compare their movement to a particular seat on the train. That seat is your Frame of Reference.

In simple terms:

The Frame of Reference is basically the thing you’re using as your stationary point to see if something else is moving. It’s often the object or place where the movement is happening or being observed from.

Motion is a relative term. Without mentioning a frame, it is meaningless. An object may be at rest and in motion as observed from different frames of reference.

Thus absolute rest and absolute motion is meaningless.

Motion Depends on What You Compare it To:

Think of motion like a comparison. You can’t just say something is “moving” without also saying “moving compared to what?”

If you don’t mention what you’re comparing it to (that frame of reference we talked about), then saying something is “in motion” doesn’t really mean anything.

Rest and Motion Can Happen at the Same Time!

Imagine this:

• You’re sitting on a train. Compared to your seat, you are at rest.
• But if someone outside the train is watching, they would say you are in motion because the train itself is moving past them.

So, the same object (you!) can be both at rest and in motion at the exact same time, just seen from different viewpoints (different frames of reference).

There is no “Absolute” Motion or Rest

Because of this, there’s no such thing as being “absolutely” still or “absolutely” moving. It always depends on your frame of reference. Motion is always relative.