1. Description of motion
Motion is a common phenomenon in the universe.
Mechanical motion: The change in the position of an object is called mechanical motion.
Reference object: The object selected as a standard when studying whether an object is moving or stationary (or an object that is assumed to be stationary) is called a reference object.
The relativity between motion and rest : Whether the same object is moving or stationary depends on the selected reference object.
2. Speed ??of movement
Speed: describes the speed of the movement of an object. The speed is equal to the distance traveled by the moving object in unit time.
Formula: v=s/t
The unit of speed is: m/s; km/h.
Uniform linear motion: motion along a straight line with constant speed. This is the simplest mechanical movement.
Variable speed motion: The speed of an object’s movement changes.
Average speed: In variable speed motion, the speed of the object during the distance can be obtained by dividing the total distance by the time taken. This is the average speed.