So after t seconds, it will increase by 0.5xm/s.

Start to rest, that is, t=0, v=0.

So v = 0.5t

V> VI

0.5t & gt VI

t & gt 12

So after 12 seconds, it exceeds 6 m/s.

v & lt=8.5

0.5t & lt=8.5

t & lt= 17

So it will not exceed 8.5 m/s in 17 seconds.