Question

A loaded train travelling at 100 m/s can decelerate at 20 m/s2. How far in advance must the brakes be applied to come to a stop?

Answer 1

Initial Velocity of the train(u)=100 m/s
Deceleration(a)=-(a) =-20m/s^2
And Final velocity(v)=0m/s
We know that,
Time(t)= v-u/t
=(0-100)/-20
=-100/-20
=5 sec.
Now, v^2=u^2+2as
where 's' denotes distance till where the train travels,
or, 0=(100)^2+ 2*(-20)*s
or, 0= 10000-40s
or, 40s=10000
or, s= 10000/40
s= 250 m.
Hence, the brakes must be applied at 250 metre in advance.

Answer 2

sorry...its t=v-u/a