Here's why:
* The equation is derived under the assumption of constant acceleration. It relies on the idea that acceleration remains the same throughout the motion.
* Non-uniform acceleration means acceleration changes with time. This violates the fundamental assumption of the equation.
* For non-uniform acceleration, you need to use calculus. You'd integrate the acceleration function to find the velocity, and then integrate the velocity function to find the displacement.
Let's illustrate with an example:
Imagine a car accelerating at a constant rate of 2 m/s². You can use the second equation of motion to find its displacement after 5 seconds.
However, if the car's acceleration is changing (e.g., increasing with time), the second equation of motion wouldn't hold true. The displacement would be different, and you'd need calculus to calculate it accurately.
In summary:
The second equation of motion is a useful tool for constant acceleration situations. But when acceleration changes with time, it becomes inaccurate and you need more advanced techniques from calculus.
