A student said, "The Earth moves around the Sun". In this context, discuss whether an object kept on the Earth can be considered to be at rest.
To determine whether an object kept on the Earth is at rest or in motion, we must first specify a reference point. As we know, the position of an object is described by its distance and direction with respect to a fixed reference point.
If we choose the Earth as our reference point, the position of the object kept on it does not change with time. Since its position relative to the Earth remains the same, the object is considered to be at rest.
However, the student correctly stated that the Earth moves around the Sun, similar to the motion of planets revolving around the Sun. If we choose the Sun as our reference point, the position of the object changes continuously with time because it is moving along with the Earth in a circular path. Thus, with respect to the Sun, the object is in motion.
Therefore, whether an object is at rest or in motion is not absolute; it depends entirely on the chosen reference point. An object can be considered at rest relative to one reference point while being in motion relative to another.
Explanation
The textbook establishes that motion and rest are relative concepts determined by the observer's frame of reference. An object is at rest if its position does not change with respect to the reference point, and in motion if it does. Since Earth revolves around the Sun, an object on Earth is stationary relative to Earth but moving relative to the Sun.
Solution Steps
Step 1: Define the role of a reference point in determining motion or rest.
Step 2: Analyze the object's state with Earth as the reference point (at rest).
Step 3: Analyze the object's state with the Sun as the reference point (in motion).
Step 4: Conclude that rest and motion are relative depending on the chosen reference point.