Question

A metro train starts from rest and in five sec-
onds achieves a velocity of 108 km/hr. After
that it moves with constant velocity and comes
to rest after travelling 45 m with uniform retar-
dation. The total distance travelled is 390 m.
What is the total time of travelling?​

Answer 1

v1=108km/hr=30m/s

v1/t1=a1

30/5

a1=4m/s²

S1=1/2at1²

S1=1/2*4*25

S1=50m

v2=v1 since constant velocity

S2=390-(S1+S3)=v2*t2

s2/v2=t2

t2=295/30

t2=9.83sec

u2/2s=a

30*30/45=a

a=-20m/s²

u=at3

30/20=t3

t3=1.5sec

total time=1.5+9.83+5

T=16.33 sec