Competing in the 100 m sprint, the runner accelerated at a uniform acceleration for 3.5 s at a distance of 20 m.

Competing in the 100 m sprint, the runner accelerated at a uniform acceleration for 3.5 s at a distance of 20 m. What result did he show over the entire distance, if after the end of the acceleration the movement was uniform?

Task data: S (length of the entire distance) = 100 m; t1 (time taken for the take-off run) = 3.5 s; S1 (take-off distance) = 20 m.

1) Speed at the end of the run (constant speed on the second part of the distance): S1 = (V + V0) * t1 / 2 = V * t1 / 2, whence we express: V = 2S1 / t1 = 2 * 20 / 3.5 = 11.43 m / s.

2) Time spent on the second part of the distance: t2 = S2 / V = (S – S1) / V = (100 – 20) / 11.43 = 7 s.

3) Result over the entire distance: t = t1 + t2 = 3.5 + 7 = 10.5 s.

Answer: The result is 10.5 s.