Question

Can the equations of motion be used in a situation where acceleration varies with time? Can they be used when acceleration is zero?

Answer 1

1. No, we cant use equation of motion if acceleration is variable.
2. We can use equation of motion in case of constant acceleration only .
3. If the acceleration is zero then we can use those equation.
4. To find the velocity or displacement in case of changing acceleration we need to integrate the acceleration with time. i.e., $\frac{dv}{dt}=a$, where $v=velocity,t=timeanda=acceleration$

Hence, we can not use equation of motion if acceleration is variable.