Un tren va a una velocidad de 72 km / h y se detiene en 4 segundos?

72km / h = 20m / s

a = v - vo / t - to ;

a = 0 - 20m / s / 4s = - 20m / s / 4s = <img src="https://tex.z-dn.net/?f=a%3D%20-5m%2Fs%5E2" />

Distancia recorrida :

d = vo.

T + (1 / 2).

A . t ^ 2

<img src="https://tex.z-dn.net/?f=d%3D%2020m%2Fs.%284s%29%2B%281%2F2%29.%28-5m%2Fs%5E2%29.%284s%29%20%5E2%3D%5C%5C%20%5C%5C%20d%3D80m%2B%281%2F2%29.%28-20m%29%5C%5C%20%5C%5C%20d%3D80m%2B%28-10m%29%5C%5C%20%5C%5C%20d%3D70m" />.