Afreight 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

80cm/s.

24cm/s.

53.3cm/s.