Question

A 70.0 kg sprinter starts a race with an acceleration of 2.00 m/s2. If the sprinter accelerates at that rate for 29 m, and then maintains that velocity for the remainder of the 100 m dash, what will be his time (in s) for the race?

Answer 1

t = 12.82s

Step-by-step explanation:

F = m×a

= (70)×(2)

= 140 N

during the acceleration, the sprinter cover d = 29 m with time:

d = 1/2×at

29 = 1/2×(2)×t^2

t^2 = 29s

t = 5.39s

and attains the velocity of:

v = a×t

= 2×5.39

= 10.77 m/s

Then,to cover the last x = 80 m with a speed of 10.77 m/s in time:

t = x/v

= 80/10.77

= 7.43s

Therefore, it will take the sprinter 7.43 + 5.39 = 12.82s