A freight train has a mass of 1.5 X 10^7 kg. If the

locomotivecan exert a constant pull of 7.5 X1^5 N, how long does it

take toincrease the speed of the train from rest to 80 km/h?

t=444.4s

Explanation:

m=1.5*10^7 kg

F=7.5*10^5 N

v=80km/h * (1h/3600s) * (1000m/1km) = 22.22m/s

Second Newton's Law:

F=ma

a=F/m=7.5*10^5 / (1.5*10^7) = 0.05m/s^2

Kinematics equation:

vf=vo+at=at

vo: initial velocity equal zero

t=vf/a=22.22/0.05=444.4s