Instantaneous velocity is given by the first derivative of distance to time i.e.
\(V_{in}=\frac{dv}{dt}\)
Here, the time interval dt is so small that it is assumed that the particle does not change its direction of motion. As a result, both the total path length and magnitude of displacement become equal over time. Therefore, instantaneous speed is always equal to instantaneous velocity.
The motion in a straight line is an object changes its position with respect to its surroundings with time, then it is called in motion. It is a change in the position of an object over time. It is nothing but linear motion.
Linear motion is also known as the Rectilinear Motion which are of two types: