Question

an Express train starts from rest and accelerates uniformly at a rate of 1 metre per second square for 20s it then maintains a constant speed of 120 seconds then the driver applies brakes and the train comes to rest in 10 seconds calculate Total distance travelled by the train​

Answer 1

Answer:507m

Explanation:make a velocity time graph in which acceleration is uniform and you see that at 6m/s×s the time is 120s and after applying brakes the te is increased by 10s = 130s .

Therefore;distance= u×t+1/2×a×t×t

Puting the terms

u=0,t=130s,a=6

<I hope it helps you>

Answer 2

s=ut+1/2at^2

:.s=0+1/2*1*20^2

=200 m

again,

v=u+at

:.v=0+1×20

final velocity after 20 secs was 20ms^-1

gvn that it maintains a constant velocity thereafter..

:.s'=v.t=20×120=2400m

now when the driver applies brakes,

u=20ms^-1

v=0m/s

t=10s

:.on applying v=u+at

we get,0=20+10a

:.a=-2m/s^2

note:the -ve sign indicates that the train is deaccelerating.

s=ut+1/2at^2

s"=20×10+1/2×(-2)×100

=200-100

=100m

:.total distance travelled

=s+s'+s"=200+2400+100=2700m

............hope it helps................