Question

Why the three equations of motion is only valid for uniform accelerated motion..?

Answer 1

The three equations of motion are valid only for uniformly accelerated motion because if acceleration keeps changing then you will not be able to put a constant value in place of 'a', rather you will have to use calculus to accomodate the change in acceleration as a function of time.

Answer 2

Answer:

The type of motion in which the object travels with a varied speed is called Non-Uniform Motion. This means that the object does not cover the equal distance in equal time intervals. ... For example, the motion of a vehicle, an oscillation of a pendulum. Non-uniform motion is also called accelerated motion.