The correct option is (c) 1 and 3 only.
Explanation
In physics, motion is the change in the position of an object with respect to its surroundings over a specific interval of time. The description of motion is fundamentally linked to a frame of reference, which consists of a reference point (origin) and a set of axes (coordinate system).
Statement-wise Analysis:
- Statement 1 is Correct: To describe the position of an object, a fixed reference point is required. In a coordinate system (such as the Cartesian coordinate system), this reference point is termed the origin. For example, describing a car as being "2 km north of the railway station" uses the station as the origin.
- Statement 2 is Incorrect: Motion and rest are relative concepts, not absolute. An object may be at rest with respect to one observer while moving with respect to another. For instance, a passenger sitting in a moving train is at rest relative to a fellow passenger but in motion relative to an observer standing on the platform. There is no state of absolute motion or absolute rest.
- Statement 3 is Correct: Motion is technically defined as a change in position of an object relative to a frame of reference as time passes. If the coordinates of the object change with time, the object is said to be in motion; otherwise, it is at rest.
Key Takeaway:
Motion is always relative to a specific frame of reference. It is defined by the change in position relative to a chosen origin over time; there is no absolute motion independent of an observer.