A body moving along straight line with uniform acceleration a has changed

its velocity from u to v then  time taken by it for this change is

Initial velocity = u

Final velocity = v

Uniform acceleration = a

Let time taken = t

We have $\frac{\text{v}-\text{u}}{\text{t}}=\text{a}$

Then $\text{t}=\frac{\text{v}-\text{u}}{\text{a}}$

i.e. time taken for change of velocity $\text{t}=\frac{\text{v}-\text{u}}{\text{a}}$ .