posted by Dennis .
A sprinter explodes out of the starting block with an acceleration of +4.1 m/s2, which she sustains for 1.2 s. Then, her acceleration drops to zero for the rest of the race.
(a) What is her velocity at t = 1.2 s.
(b) What is her velocity at the end of the race?
v = at = 4.1 * 1.2 = 4.92m/s
speed remains constant after that.