Problem data: L (mountain length) = 40 m; t (duration of descent of the athlete in question) = 5 s.
1) Find the speed of the athlete in question at the end of the descent: S = L = (V + V0) * t / 2 = (V + 0) * t / 2, whence we express: V = 2L / t = 2 * 40/5 = 16 m / s.
2) We calculate the acceleration of movement: V = V0 + a * t = 0 + a * t, from where we express: a = V / t = 16/5 = 3.2 m / s2.
Check: S = L = (V ^ 2 + V0 ^ 2) / 2a = (16 ^ 2 – 0) / (2 * 3.2) = 40 m (correct).
Answer: The athlete moved while descending the mountain with an acceleration of 3.2 m / s2 and had to pick up a speed of 16 m / s.
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