A freight train has a mass of 3.1 × 107 kg.

Question

If the locomotive can exert a constant pull
of 4.9 × 105 N, how long would it take to
increase the speed of the train from rest to
71.9 km/h? Disregard friction.

Answer 1

a=F/m=4.9*10^5 / 3.1*10^7=0.0158 m/s^2.

V = 71.9km/h = 71900m/3600s = 20 m/s.

t = (V-Vo)/a = (20-0)/0.0158 = 1265.8 s.
= 21 min.