A particle moving with velocity v has gained uniform retardation a then

$\text{ it's average velocity will become }\frac{\mathrm{v}}{2}\text{ as it comes at rest }$

$\text{ it's final velocity will become zero after }t=\frac{v}{a}$

it’s average velocity will become v as it comes to rest

$\text{ it's final velocity will be zero after }t=\frac{v}{2a}$