In physics, an object is at rest if it does not change its position compared to its surroundings over time.

If you leave a book on your desk and walk away, the book is at rest because its position relative to the table stays the same. Motion occurs when an object changes its position continuously as time passes. If you throw a ball, it is in motion because it moves from your hand to a different spot in the air.

The Concept of Frame of Reference

A frame of reference is the perspective or the point of view from which you observe motion. Imagine you are sitting inside a moving train. To you, the person sitting across from you is at rest. However, to a person standing outside on the platform, both you and the person across from you are in motion. Because your observation changes based on where you are standing, your frame of reference defines whether something is moving or still.

Relative Nature of Motion

Motion is always relative. Nothing in the universe is truly at absolute rest. Even if you are standing still on the ground, the Earth is spinning and moving around the Sun. This means you are actually moving at a very high speed through space. We call an object at rest only when its position does not change with respect to nearby objects like trees, buildings, or roads.

• Reference Point: This is a fixed object or location used to judge if another object is moving.
• Observer: The person or instrument measuring the change in position.
• State of Motion: An object's condition of being either still or moving based on the observer's location.

Dimensions of Motion

Motion happens in different ways depending on the space available:

• One-dimensional: An object moves in a straight line, like a car on a flat, straight road.
• Two-dimensional: An object moves on a flat surface or plane, like a bug crawling on a table.
• Three-dimensional: An object moves through space, like a bird flying or an airplane climbing in the sky.