A body is said to be in motion if it changes its position with respect to time.
Types of Rectilinear or Linear Motion
- Non-Uniform linear motion with non-zero acceleration or variable velocity
- Uniform linear motion with zero acceleration or constant velocity
The simplest type of one-dimensional motion is Linear motion. As per Newton's first law of motion, an object will either be in rest or continue to move in a straight line with a uniform velocity unless and until an external force is applied to it.
Linear motion is a one-dimensional motion but in general, the motion has both magnitude and direction, i.e. an object's position and velocity are described in vector quantities.
Uniform Motion in a Straight Line
A body is said to be in a uniform motion if it travels in a straight line covering equal distances in equal intervals of time. A body is said to have uniform acceleration if the rate of change of its velocity remains constant.
Non-uniform Motion in a Straight Line
A body is said to have a non-uniform motion when the velocity of a body changes by unequal amounts in equal intervals of time. While in movement, the rate of change of its velocity changes at different points of time.
Path Length: The path length is the total length of the path that has to be traversed by the object.
Displacement: Displacement is the change in position of a body. The magnitude of displacement between the same points is proportional to the path length.
Uniform Motion: When the displacement of an object is equal in equal time intervals, the motion is said to be uniform, else it is referred to as non-uniform.
Average Speed: Average speed is referred to the ratio between the total path length traversed to the time taken.
Instantaneous Velocity: It is the velocity when the limit of the average velocity has an indefinitely smaller interval of time.
Average Acceleration: It is the change in velocity corresponding to the time interval with in which the change has accelerated.