A sprinter explodes out of the starting block with an acceleration of +2.79 m/s2 , which she sustains for 1.65 s. Then her acceleration drops to zero for the rest of the race. What is her velocity at t = 1.65 s and at the end of the race?

Answer 1

For the velocity at t = 1.65 s, use

v = a t = 4.60 m/s.

Since there is no acceleration or deceleration after that, 4.6 m/s remains the velocity.