Question

Brakes are applied to a train travelling at 72 km/hr. after passing 200m its velocity is reduced to 36 km/hr. at the same rate of retardation how much further will it go before it is brought to rest

Answer 1

u=72km/h = 20 m/s
v=36km/h=10m/s
s(distance)=200m
using formula
v^2=u^2+2as
a(accerlation)=0.75m/s^2
now we have to find the train travel further when the brake apply so at last it v=10 m/s
so using formula 
v^2=u^2+2as
s=v^2/2.g 
s=100/2.0.75
s=66.67 
appox 67 is answer