If a train travelling at 72 kmph is to be brought to rest in a distance of 200 metres, then its retardation should be
20 ms-2
10 ms-2
2 ms-2
1 ms-2
u=72kmph=20m/s,v=0By using v2=u2−2as⇒a=u22s=(20)22×200=1m/s2